abbreviations:

dp: double-positive

sp: single-positive

PP: Peyer's patches of the small intestine(duodenum, jejunum)

IEL: intraepithelial lymphocytes of the small intestine(duodenum, jejunum)

tLN: tracheobronchial lymph node

mLN: mesenteric lymph node

Faculty of Veterinary Medicine

PRINTED IN THE DATA PROCESSING CENTER, UNIVERSITY OF LEIPZIG

Characterization of canine CD4+CD8α+ double-positive (dp)T cells in lymphatic and non-lymphatic organs

Friederike Rabigera, Doris Bismarcka,b, Martina Protschkaa, Peter F. Moorec, Mathias Büttnera, Heiner von Buttlara,d, Maria Eschkea, and Gottfried Albera

a I n s t i t u te o f Immuno logy/Molecu la r Pa thogenes i s , Cen te r fo r B io techno logy and B iomedic ine , Co l l ege o f Ve te r ina r y Med ic ine , Un i ve r s i t y o f Le ipz ig , Germanyb presen t addres s : Labok l in GmbH & Co. KG, Bad K i s s ingen , Germany

c Depar tmen t o f Ve te r ina r y Pa tho logy, Mic rob io logy and Immuno logy, Schoo l o f Ve te r ina r y Med ic ine , Un ive r s i t y o f Ca l i f o rn ia , Dav i s , Un i ted S ta tes d presen t addres s : Bundeswehr I n s t i t u te o f Mic rob io logy, Mun ich , Germany

are mature extrathymic T cells with a frequency of ~ 2% of all T cells

originate from both CD4+ and CD8α+ single-positive (sp) T cells, but CD4+ sp T cells are the more potent progenitors

have features of activated T cells (≥ 50% CD25+)

Analysis of CD4+CD8α+ double-positive T cells in lymphatic and non-lymphatic organs of the dog

Canine CD4+CD8α+ dp T cells are present in secondary lymphatic organs as well as in non-lymphatic tissues.1 Canine double-positive T cells are mature T cellslacking the thymic marker CD1a.

CD4+CD8α+ dp T cells of lymphatic and non-lymphatic tissue predominantly display a CD8αα phenotype in contrast to CD8α+ sp T cells and CD4+CD8αβ+ thymocytes.

Similarly to blood, CD4+CD8α+ dp T cells in different organs are mainly CD25+.

CANINE CD4+CD8α+ DOUBLE-POSITIVE (DP) T CELLS OF THE PERIPHERAL BLOOD

Only in LN and PP a minority of CD4+CD8α+ dp T cells expresses Foxp3.

CD4+CD8α+ dp T cells are present in secondary lymphatic and non-lymphaticorgans.

Conclusions

All dp T cells are mature CD4+CD8αα+ T cells indicating an extrathymic origin.

Further investigations are needed to clarify the functional role of this exceptional T cell population in health and diseases of dogs.

Dp T cells constitutively express more CD25 than their CD4+ sp and CD8α+ sp counterparts characterizing them as activated T cells. Underlining the exceptional features of the gut immune system, these findings can not be confirmed for the intestinal intraepithelial lymphocytes.

In the Peyer’s Patches more CD4+CD8α+ dp T cells than in any other analyzed organs could be found, which might be a hint to unique migratory properties in mucosa-associated lymphatic tissue.

AIM OF THE STUDY

RESULTS

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Only the IEL fraction of dp T cells constitute an exception, as there is no significantdifference between the sp and the dp subpopulations regarding their CD25 expression.

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AL 371/8-3

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