immunological studies in acquired immunodeficiency syndrome

Scand. J. Immunol. 23, 669-678, 1986

Immunological Studies in the AcquiredImmunodeficiency Syndromen . Active Suppression or Intrinsic Defect—Investigated by Mixing AIDS Cells withHLA-DR Identical Normal Cells

B. HOFMANN, N. 0DUM, B. K. JAKOBSEN, P. PLATZ, L. P. RYDER,J. O. NIELSEN, J. GERSTOFT & A. SVEJGAARDTissue Typing Laboratory of the Department of Ctinical Immunology, State University Hospital,(Rigshospitalet) of Copenhagen, Denmark.

Hofmann, B., 0dum, N., Jakobsen, B.K., Platz, P., Ryder, L.P., Nielsen, J.O. Gerstoft, J. &Svejgaard, A. Immunological Studies in the Acquired Immunodeficiency Syndrome. II. ActiveSuppression or Intrinsic Defect—Investigated by Mixing AIDS Cells with HLA-DR IdenticalNormal Cells. Scand. J. Immunol. 23, 669^678, 1986

The lymphocyte transformation responses to mitogens (phytohaemagglutinin (PHA),concanavalin A (Con A), and pokeweed mitogen (PWM)), allogeneic cells, and theantigen-purified protein derivative (PPD) were studied in six acquired immunodeficiencysyndrome (AIDS) patients and in six healthy controls, each of whom was HLA-DR- andmixed lymphocyte culture (MLC)-identical with one of the AIDS patients. No evidence ofsuppression was observed when irradiated or non-irradiated AIDS peripheral bloodmononuclear cells (PBMC) were added to cultures of HLA-DR-identical PMBC fromhealthy controls stimulated with the strong mitogens PHA and Con A or with allogeneiccells, but suppression may be involved in the decreased responses in cultures stimulated withPWM or PPD. Addition of supernatants from macrocultures of AIDS cells did not suppressresponses of control PBMC. Thus, suppression by any lymphocyte subset or soluble factoralone cannot explain the generally severely depressed transformation responses in AIDS.Addition of heavily irradiated HLA-DR-identical PBMC from healthy controls or super-natants from these cultures led to increased responses in cultures of mitogen-stimulatedAIDS PBMC and in some cultures of antigen or allogeneic cell-stimulated AIDS PBMC,which were of the same magnitude as seen after the addition of commercially obtainedT-cell growth factor (TCGF). This indicates that AIDS cells are deficient in producingTCGF.

Heavily irradiated AIDS PBMC were capable of restoring the transformation responsesto mitogens and antigens of purified HLA-DR-identical normal T cells, indicating thatAIDS cells have a normal antigen-presenting capacity and interleukin (IL-1) production.However, AIDS PBMC had a very poor capacity to stimulate normal PBMC in MLC.Together, our experiments suggest that the immune deficiency in AIDS cells may bepartially due to a decreased capability of T lymphocytes to produce TCGF and that adecreased number and/or function of dendritic cells may also be involved.

Bo Hofmann, Tissue Typing Laboratory, 7631 State University Hospital (Rigshospitalet)Tagensvej 18-20 DK-2200 Copenhagen N, Denmark

Peripheral blood mononuclear cells (PBMC) antigens in the lymphocyte transformation testfrom patients with the acquired immunodefi- [3, 12]. Part of this abnormality is undoubtedlyciency syndrome (AIDS) and the AIDS- due to a pronounced decrease in the numberrelated complex (ARC) often preceding AIDS of circulating T4-positive (helper) cells, whichare characterized by a severely decreased or in healthy individuals are responsible for theabsent response in vitro to mitogens and major part of the response to mitogens and the

669

670 B. Hofmann et al.

entire response to antigens [14, 15, 20].However, even when the number of T4-positive cells is adjusted to normal values, theresponse is still considerably decreased [1, 14],which indicates that the decreased responsive-ness cannot solely be due to low numbers ofT4-positive cells. A smaller number of theT4-positive cells in patients with AIDS areknown to be infected with the human T-cellleukaemia virus (HTLV III) [4, 9, 16, 22].AIDS PBMC contain a high proportion ofT8-positive 'suppressor' cells, and it might bespeculated that these cells suppress the re-sponse of the T4-positive cells. However, wefound no evidence of suppression when weadded T8-positive to T4-positive AIDS PBMC[14, 20]. Moreover the T8-positive AIDS cellsthemselves appear to be abnormal, since T4-depleted (i.e. T8-enriched) AIDS PBMC didnot provide the response to mitogens seen insimilar suspensions from healthy individuals[14]. We concluded that the low to absentresponse of AIDS PBMC, apart from the lownumber of T4-positive cells, may be due to (i)defects of both T4- and T8-positive cells (ii)suppression due to T8-negative cells or tosoluble substances not excluded by our pre-vious experiments, and/or (iii) defects in theaccessory cells.

The present experiments were undertaken inorder to explore which of the above possibili-ties were involved.

METHODS

Patients. All the patients included in the studywere homosexual men aged 27 to 54 years admittedto the University Clinic for Infectious Diseases inCopenhagen. All the AIDS patients fulfilled thecriteria for AIDS given by the Center for DiseasesControl, Atlanta, Georgia, USA.

Six patients with AIDS were included in the'cell-mixing' experiments (Tables I-III). These sixpatients were chosen because they were the onlyavailable patients found to have two well-definedHLA-DR antigens and to be HLA-DR-identical andmixed lymphocyte culture (MLC)-negative with anindividual from a control group of 250 DR-typedhealthy individuals. The MLC experiments wereperformed like a chessboard including cells fromother AIDS patients and haplo-DR-identical andnon-DR-identical cells. Among these six patients,patient no. 3 had Kaposi's sarcoma, while the othershad pneumonia due to Pneumocystis carinii. Wewere only able to obtain small numbers of lympho-

cytes from patients nos 4 and 6 because of theirciinical condition. Patients nos 4 and 5 were newlydiagnosed when the lymphocytes were collected.Patients nos 1, 2, 4, and 6 have subsequently died.Each pair of HLA-DR-identical AIDS patient/healthy control is given the same number in all thetables.

Besides AIDS patients nos 2 and 3, five additionalAIDS patients and six patients with ARC wereincluded in the study of MLC response and stimula-tory ability (Fig. 2). One of these additional AIDSpatients had Kaposi's sarcoma, two had pneumoniadue to Pneumocystis carinii, one had Cryptosporidiumenterocolitis and choriorenitis due to Cytomegalo-virus, and the last patient had a systemic infectionwith Mycobacterium avium intracellulare. Among thesix patients with ARC, five had lymphadenopathywith periodic fever and weight loss. One wasHBsAg- and HBeAg-positive and one had ashigellosis of long duration. Only one of the sixpatients was without symptoms at the time ofinvestigation.

Healthy controls. Thirteen volunteers from amongmale medical staff and healthy blood donors servedas normal healthy controls. Six of these donors wereselected because they were HLA-DR identical andMLC-negative to a corresponding AIDS patient.

Isolation, freeezing, and thawing of lymphocytes.PBMC were isolated by lymphoprep (Nyegaard,Oslo, Norway) density gradient centrifugation [5].PBMC were suspended to 6x10*̂ ml in freezemedium (15.5 ml RPMI), 2.5 ml heat-inactivatedpooled male serum (HS) and 2 ml dimethylsulphox-ide (Merck, Munchen, FRG), and frozen in 1-mltubes by gradient freezing (Cryoson) to -80°C andthen stored in liquid nitrogen. When thawed, thecells were placed in a 37°C water bath and, afterthawing, were immediately washed twice in RPMIwith 15% HS. Adherent cell-depleted T lymphocyteswere isolated by passing PBMC twice thi'ough nylonwool [14]. Briefly, 10 million thawed PBMC weresuspended in RPMI 1640 (Gibco, Grand Island,N.Y., USA) supplemented with antibiotics and 15%HS, and allowed to incubate in a 10-ml syringe with2 g of washed nylon wool for 2 h at 37°C. T cellswere eluted from the column by washing with 20 mlof RPMI at 37°C.

Microcuttures. Cultures were prepared in triplicatein 0.35 ml round-bottomed plastic microtitre plates(Greiner, Nurtingen, FRG). Each culture contained50,000 responder PBMC. Fifty thousand DR-identical normal cells were added to some cultures ofpatient cells. In all cultures, the total volume was170 fi\ RPMI 1640 (Gibco), supplemented withantibiotics and 15% HS. The mitogen or antigenamounts per well were: phytohaemagglutinin (PHA,Difco, Detroit, Mich., USA) 20 fig and 2 fig,concanavalin A (Con A, Pharmacia, Uppsala,Sweden), 10 fig, pokeweed mitogen (PWM, Gibco),20 fi\ of a 1:50 suspension, and purified proteinderivative, (PPD, Statens Seruminstitut,Copenhagen, Denmark), 2 fig. In MLC experiments5x10'' frozen irradiated allogeneic cells pooled frommore than four donors were used as allo-antigeneic

Immunological Studies in AIDS II 671

stimulus. The stock solution of T-cell growth factor(TCGF) (Lymphocult-TLF, Biotest, Dreiich, FRG)was diluted 1:4 and used in amounts of 50 //I per well.The amount of PHA in this dilution corresponded to3.7 ng per well. One mieroeurie [H'] thymidine wasadded after 72 h (mitogens) or after 120 h (antigens),and the cells were collected 24 h later on glass fibre

filters on an automatic harvesting machine (Skatron,Lierbyen, Norway), and the incorporated radioactiv-ity was measured in a liquid scintillation counter(Beckman LS 1800) after the addition of 1.5 mlscintillation fluid. The results are given as medians oftriplicate determinations. Non-conclusive triplicateswere excluded. In Tables I and II the values in cpm of

TABLE I. The effect of AIDS PBMC on the transformation responses of HLA-DR-identical PBMC fromhealthy controls

Responder cells

PHA-2

Con A

PWM

Pooledallogeneiccells

PPD

1*23456

Median

123456

Median

123456

Median

12356

Median

12356

Median

AIDS PBMC

Non-irradiated

0.8t4.99.8

47.726.485.0

18.1

0.724.778.818.5

-4.947.5

21.6

0.65.34.71.5

-6.85.0

3.1

0.52.20.62.1

11.1

2.1

0.51.40.6

-0.20.1

0.5

Normal PBMC

9.046.822.584.656.4

223.4

51.6

30.9112.3187.375.387.3

147.9

99.8

11.828.069.238.614.264.8

33.3

15.98.1

13.523.962.0

15.9

13.068.734.719.747.9

34.7

Suppressor index %Normal 1PBMC with

addition of AIDS PBMC

Irradiated

6712110513352

108

107

15510576

16785

128

117

8210764625658

63

3110043

15042

43

2326899514

26

Non-irradiated

587587

1559655

81

1499353

14711386

103

14511710010911782

117

5113551

12579

79

2265557

87

55

*The numbers indicate a pair of HLA-DR identical healthy control/AIDS patient.tEntries are: cpm increment over corresponding unstimulated values, divided by 1000.The unstimulated cultures of mixtures of normal PBMC and AIDS PBMC (non-irradiated) gave a

median response of 2.7x10-' cpm (range 1.5-6.5) after 96 h and a median response of 1.9x10^ cpm(range 0.7-8.5) after 144 h. Suppressor index=(cpm of mixture of AIDS PBMC and normalPBMC)/cpm of normal PBMC. If the AIDS PBMC added were non-irradiated the response of theAIDS PBMC was subtracted from the response of the mixtures before the suppressor index wascalculated.

43


TABLE II. The effect of strongly (7,500 rad) irradiated PBMC from healthy controls or TCGF on thetransformation responses of HLA-DR-identical PBMC from patients with AIDS

Responder cells:

PHA-2

Con A

PWM

Pooledallogeneiccells

PPD

Addition

1*2345

Median

12345

Median

12345

Median

12345

Median

12345

Median

None

0.8t4.99.8

37.187.8

9.8

0.724.778.82.2

19.9

19.9

0.65.34.70.15.7

4.7

0.52.20.63.8

25.9

2.2

0.51.40.60.10.6

0.6

AIDS

ControlPBMC

1.119.126.261.999.0

26.2

2.043.390.3

7.240.0

40.0

2.38.4

21.13.1

20.8

8.4

0.75.71.37.4

24.7

5.7

1.118.010.2

-0.2-0.4

1.1

PBMC

TCGF

4.113.545.357.696.2

45.3

11.130.075.113.093.0

30.0

2.06.9

15.22.2

36.6

6.9

1.75.13.03.8

119.0

3.8

1.73.9

13.9-1.9123.0

3.9

IrradiatednormalPBMC

0.61.54.66.49.8

4.6

0.81.71.97.2

-6.4

1.7

0.92.12.52.2

-2.7

2.1

0.50.51.54.04.4

1.5

0.51.31.00.20.4

0.5

*The numbers indicate a pair of HLA-DR-identical AIDS patient/healthy control.tEntries are: cpm increment over corresponding unstimulated values, divided by 1000.The unstimulated cultures of mixtures of AIDS PBMC and irradiated normal PBMC gave a median

response of 0.7x10' cpm (range 0.3-2.9) after 96 h and a median response of 0.7x10' cpm (range0.4-1.2) after 144 h. A response is regarded as increased if the response of the mixture was higherthan the sum of the response of AIDS PBMC and the response of the irradiated normal PBMC.

the unstimulated responses have been subtracted. InTable I the suppressor index has been calculated as theresponse in cpm of the culture of normal PBMC withAIDS PBMC added, divided by the response in cpm ofthe normal PBMC. If the AIDS PBMC were non-irradiated, the responses of these cells were subtractedfrom the responses of the normal PBMC culture withAIDS PBMC added before the suppressor index hadbeen calculated. In Table II the responses of the AIDSPBMC after addition of HLA-DR-identical normalPBMC were regarded as increased if the response ofthe mixture was higher than the sum of the response of

AIDS PBMC and the response of the irradiatednormal PBMC.

Macrocultures. Cultures were prepared in 10 mlround-bottomed tubes. Each culture contained fourmillion cells in the same dilution and with the sameconcentration of PHA, Con A, or PWM as describedfor microcultures. An unstimulated control culturewas also included.

Medium exchange assay. Every 12 h, a sample of500 fi\ supernatant was taken from each macrocul-ture, and depleted for cells by centrifugation (Fig.4). Simultaneously, 50 fi\ supernatant from the


microcultures of PBMC from AIDS patients or fromhealthy controls, was gently removed from the top ofeach microtitre well and discarded. Instead of thediscarded supernatant, 50 fi\ of the supernatant frommacrocultures of PBMC from AIDS patients or fromhealthy controls was added.

DR typing. The method agreed on for the 7thInternational Histoeompatibility Workshop (Bod-mer, FRG, 1977) was used for DR-typing. At leasttwo different anti-DR sera were used for each of thefollowing specificities: DR 1, 2, 3, 4, 5, 7, w8, w9,and wlO. DR w6 was defined by sera containinganti-DR l+2+w6 and by anti-DR w52 and anti-DQwl sera.

Statistical methods. The Wilcoxon matched-pairssigned ranks one-tailed test was used.

RESULTS

All 17 patients, except one AIDS patient withKaposi's sarcoma, had a helper to suppressor-cell ratio of less than 0.9. All had a decreasedabsolute number of helper cells (<0.5xl0'/l),and severely decreased or absent responses toantigens and mitogens on repeated investiga-tions, i.e. less than 50% response comparedwith the two simultaneously investigated heal-thy controls for at least two of the the threemitogens: PHA, Con A, and PWM (data notshown). A certain diversity was found amongthe ability of patient cells to respond tomitogens and antigens, due to differences inthe clinical condition of these patients. Thehighest responses were found in patients withthe shortest duration of the disease.

Table I shows the effect of adding AIDSPBMC to cultures of DR-identical healthycontrol PBMC, subsequently stimulated withmitogen, antigen, or an allogeneic pool. Theadded AIDS PBMC were either non-irradiatedor irradiated with 7500 rad. The responses ofunstimulated mixtures of PBMC from pairs ofHLA-DR-identical controls and AIDS patientsafter 144 h (2.9, 1.8, 0.7, 1.9, and 8.5xlO-* cpm) are compatible with' close MLCsimilarity. Addition of irradiated AIDS PBMCdid not suppress the response of normalPBMC stimulated with PHA (suboptimal con-centration). Con A, or a pool of allogeneiccells, but the responses to the antigen PPDwere decreased in all five experiments and theresponses to PWM were decreased in five outof six experiments. The suppressive properties

were the same for non-irradiated AIDSPBMC, which, moreover, did not suppress theresponses to PWM.

Table II shows the transformation responsesof AIDS PBMC to (i) the mitogens PHA, ConA, and PWM (ii) the antigen PPD, and (iii)allogeneic cells, after addition of heavily irradi-ated (7500) DR-identical healthy controlPBMC or TCGF. The results show a diversitybetween the responding capacities of PBMCfrom different AIDS patients. The responsesof patient no. 1, which were very low atrepeated investigations, were not or onlyslightly increased by the addition of normalirradiated PBMC. The four other patients hadhighly increased responses to at least two ofthe three mitogens PHA, Con A, or PWM.The response to allogeneic cells was onlyincreased in patients nos 2 and 3 to a higherresponse than the sum of the response ofAIDS PBMC and the response of the irradi-ated normal PBMC. When TCGF was addedto cultures of AIDS PBMC, increases in re-sponses of about the same magnitude wereobtained. No further increases were seen,when HLA-DR-identical healthy controlPBMC and TCGF were added at the sametime (data not shown). If the responses of themixtures are compared with those of normalPBMC in Table I, the increased responses ofAIDS PBMC are still subnormal. When super-natants from mitogen-stimulated macrocul-tures of simultaneously run non-DR or DR-identical control PBMC are added to culturesof mitogen-stimulated AIDS PBMC, the in-creases in the responses were equivalent to theincreases obtained after addition of irradiatednormal PBMC (data.not shown).

Table III shows that the mitogen responsesof adherent-cell depleted T cells from healthycontrols were normalized both when auto-logous irradiated PBMC and when irradiatedHLA-DR identical AIDS PBMC were added.Six parallel experiments were performed be-tween pairs of HLA-DR-identical normal con-trols with similar results (data not shown).Analogous experiments were carried out withthe antigen PPD, but only two of the fourhealthy controls used in the experiments withAIDS PBMC responded well to PPD. In thesetwo experiments both AIDS PBMC and thecontrols' own PBMC could increase the re-sponse to PPD, although none of the responses


TABLE IIL The ability of irradiated PBMC from AIDS patients to restore the transformation responses ofHLA-DR-identical T cells from healthy controls

PHA,1*235

PHA,1234

PWM1234

PPD35

DR type

suboptimal concentration2,62,72,32, 2t

Median

optimal concentration2,62,72,32,2

Median

2,62,72,32,2

Median

2,32,2

Transformation responses of healthy controls, cpmx 10 ^

PBMC

2.113.217.943.9

15.6

47.7113.070.3

148.8

91.7

5.020.619.515.2

17.2

23.116.8

None

1.53.90.87.1

2.7

35.788.045.1

105.2

66.6

0.37.40.46.1

3.3

2.70.3

T cells with addition

Irradiatedown PBMC

5.89.9

16.958.9

13.4

43.8104.581.5

120.8

93.0

0.97.67.2

14.8

7.4

5.04.7

of

IrradiatedDR-identicalAIDS PBMC

9.522.96.6

38.2

16.2

64.5108.054.8

118.3

86.3

2.411.33.0

13.8

7.2

6.82.3

*The numbers indicate a pair of HLA-DR-identical AIDS patient/healthy control,t Known to be homozygous.The unstimulated cultures of mixtures if control T cells and irradiated AIDS PBMC gave a median

response of 1.0x10^ cpm (range 0.5-1.5).

were increased to the same magnitude as theantigen responses of normal PBMC.

Figure 1 shows that mitogen-stimulated mic-rocultures of healthy control PBMC were notsuppressed by supernatants from simultane-ously run macrocultures of AIDS PBMC. Thesame results were found for cultures stimulatedwith PWM (data not shown). In three of theexperiments, the supernatants came from mac-rocultures of DR-identical AIDS PBMC, butthis did not seem to alter the results.

Figure 2 shows that irradiated PBMC fromAIDS patients and patients with ARC canstimulate PBMC from healthy controls inMLC, but clearly to a significantly lowerresponse (/'<0.01) than that obtained whenstimulated with irradiated PBMC from healthycontrols. The responses of PBMC from AIDSpatients and patients with ARC were also

significantly lower (/'<0.05 and P<0.01) whenstimulated with irradiated PBMC from patientsthan when stimulated with irradiated PBMCfrom healthy controls. Patients with ARCseem to constitute an intermediate group asregards both stimulating and responding capac-ity in MLC.

DISCUSSION

The above experiments aimed at clarifying themechanisms behind the low responses of AIDSPBMC to mitogens and antigens in the in vitrolymphocyte transformation test by studying thecapabilities (i) of AIDS PBMC and super-natants of stimulated cultures of such cells tosuppress the responses of PBMC from healthy

PHA-2


PHA-20cpm X 10

100-

5 0 -

Addition ofsupernatant from:

cpm X 10"

100-

50-

none normalPBMCmacro-culture

AIDSPBMCmacro-

culture

• (180) .(IS?)

normal AIDSPBMC PBMCmocro- macro-culture culture

FIG. 1. Transformation responses of PBMC from normal controls stimulated with PHA insuboptimal concentration (left) and in optimal concentration (right). From each microweil(nOfil) SOfil supernatant was removed every 12 h and replaced by 50fil of supernatant froma macroculture of PBMC from either the control person or a patient with AIDS. Medianvalues are indicated by a bar.

cpm X 10

60-

- 3

40H

o V

2 0 -

Stimulators

Responders

1

1AIDS

••

1ARCAIDS

•

•

•

1Normal

: :•• •

•

AIDS ARC

ARC

V

.\

TNormal

•

•••••

.If:

AIDS

•••

.

1ARC

#i•••

1Normal

Normal ceils

FIG. 2. MLC responses of PBMC from patients with AIDS (N=7), patients with ARC (^=6),and normal controls (^=5) stimulated with irradiated PBMC from one of the same threegroups. Median values are indicated by a bar.

individuals (ii) of irradiated PBMC from heal-thy individuals and/or TCGF to restore theresponses of AIDS PBMC (iii) of AIDSPBMC to present mitogen and antigen to

purified T cells from healthy individuals, and(iv) of AIDS PBMC to stimulate and respondin MLC.

In order to avoid possible interference by


simultaneous MLC reaction when mixingallogeneic cells, we selected all available pairsof AIDS patients and healthy controls whoshared both HLA-DR antigens and who didnot respond to each other in MLC. Whenirradiated AIDS PBMC were added to culturesof DR-identical control PBMC, no suppressionwas found in cultures stimulated with themitogens PHA and Con A or with allogeneiccells, whereas suppression was observed incultures stimulated with the antigen PPD andperhaps also in cultures stimulated with theweaker mitogen PWM (Table I). The suppres-sive properties of the AIDS PBMC were notincreased if the AIDS PBMC added werenon-irradiated, indeed the suppression of thePWM response was abolished. This can beexplained by responses of the non-irradiatedAIDS cells induced by TCGF produced by thenormal PBMC. Supernatants from simul-taneously run AIDS macrocultures did notsuppress the response of healthy controlPBMC stimulated with mitogens (Fig. 1).

These results indicate that suppression byany cell subset or factor alone cannot explainthe severely decreased lymphocyte transforma-tion response to the strong polyclonally acti-vating mitogens and alloantigens in AIDS, butthey do not rule out that the decreased orabsent responses to the weakly stimulatingmitogen PWM and to antigens might be par-tially explained by cellular suppression or cyto-toxicity. Others have reported a suppressivefactor in serum from patients with AIDS [8,17], produced by cells infected with HTLV III,but this suppressive factor was not found inour experiments with supernatants from cul-tures of AIDS PBMC.

The addition of irradiated DR-identicalhealthy control PBMC to cultures of AIDSPBMC led to an increase in most of thetransformation responses of the latter tomitogens and to an increase of some of theresponses to antigens and allogeneic cells.Increases of responses of the same magnitudewere obtained when TCGF was added tocultures of AIDS PBMC, whereas no addition-al effects were seen when both TCGF andDR-identical PBMC were added simultaneous-ly. There seems to be a certain diversitybetween the responding capacity of PBMCfrom different AIDS patients, since the re-sponses of patient no. 1 could not be increased

or only slightly, in all cultures on repeatedinvestigations, while the responses of the fourother patients could be increased in most ofthe mitogen-stimulated cultures.

The observation that TCGF and DR-identical allogeneic PBMC induces equivalentincreases in the proliferative responses indi-cates that the allogeneic cells act through theirproduction of TCGF. It also indicates thatfactors other than TCGF produced by theallogeneic normal cells do not further increasethe responses of AIDS PBMC. A decreasedproduction of TCGF is in accordance withother reports [6, 7, 18, 19, 21, 23], showingthat TCGF can increase the transformationresponses of AIDS cells.

Irradiated DR-identical PBMC from bothcontrols and AIDS patients normalized theresponse of adherent cell-depleted T cells fromhealthy controls (Table III), indicating thatcells from AIDS patients can 'present'mitogens and probably also antigens to normalDR-identical T cells, and that the interleukin 1(IL-1) production is normal. This agrees withrecent observations by C. Enk, Clinic of Infec-tious Diseases, State University Hospital,Copenhagen (pers. comm.), who found a nor-mal production of IL-1 from AIDS cells in afunctional assay. Indeed, the antigen-presenting cells represent the first mononu-clear cell subset from AIDS patients that wehave found to be normal. The antigen-presenting capacity of irradiated PBMC mostlikely comes from monocytes, since the capa-city of B cells to present antigen is lost afterirradiation [1].

The apparently normal accessory cell func-tion for mitogens and antigens of AIDS PBMCis in striking contrast to the severely impairedcapability of these cells to stimulate in MLC(Fig. 2). This discrepancy might be due to adecreased number or function of dendritic cells[2, 10, 11], but this possibility remains to beexplored.

In conclusion, the severely decreased re-sponsiveness of AIDS PBMC in the lympho-cyte transformation test seems to be due todeficient accessory-cell function or to suppres-sion by any cell subsets or soluble factors(except perhaps for the response to antigens).Apart from the low number of T4-positivecells, an inadequate production of TCGF byAIDS T lymphocytes seems to contribute to


the deficient lymphocyte transformation re-sponse in AIDS cells.

ACKNOWLEDGMENTS

This work was supported in part by the DanishMedical Research Council and by the DanishCancer Society.

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23 Sherudan, J., AureHan, L., Donnenberg, A. &Quinn, T. Cell-mediated immunity to cytomega-lovirus and Herpes simplex virus antigens in the Received 9 September 1985acquired immune deficiency syndrome. Inter- Received in revised form 27 December 1985

immunological studies in acquired immunodeficiency syndrome

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