the adaptive immunity part 3-au 10-1.pdf

8/8/2019 The Adaptive Immunity Part 3-AU 10-1.PDF

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The Adaptive Immunity

Chapter 17



Immunoglobulins / Antibodies

1. Antibodies are proteins made in response toan antigen that can bind with that antigen(highly specific)

2.

A single antibody unit is a monomer which is bivalent

3. Five types / classes of antibody: may have different numbers of binding sites



Basic structure of Antibody

1. A typical antibody

monomer has four proteinchains:

two heavy + two lightchains (disulfide links)

2. Within each chain is

a variable region (V) and

a constant region (C)



3. A var iable region (V) is where antigen binding

occ

urs.

4. A constant region (Fc)serves as a basis forc

lass

ifying antibody.

5. The Fc region can attach toa host cell or a complement



Classes of Immunoglobulins

1. IgGa) about 80% of total serum

antibody

b) predominant antibody ofsecondary humoralresponse

c) crosses the humanplacenta to produce natural, passive, acquired immunity

d) valency is 2

2. IgMa) found in serum, lymph

and on B-cell surfaces

b) fi rst & predominantantibody of pr imaryhumoral response

c) pentamer ; valency is 10



4. IgD

a) minor serum antibodyb) found on B-cell

surfaces: presumedantigen receptors on

B lymphocyte surfaces

c) no known function inserum;

d) valency is 2

5. IgE

a) 0.

002% ofse

rumantibody; generallynot ci rculating

b) most bound tightly by

F c region to mast cells c) participate in allergic

reactions

d) valency is 2



Protective Outcome of

Antibody-Antigen Binding

1. Neutralization

2.

Immobilization and pre

ve

ntion ofAdherence

3. Agglutination and Precipitation

4.

Ops

onization5. Complement Activation



Figure 17.7



Vaccines

1. Heat-killed / Inactivated vaccines

2. Attenuated vaccines

3.

Toxoid vacc

ines

4. Subunit vaccines



Adaptive Immunity

Humoral vs. Cell MediatedResponses



Cell Mediated Immunity

1) Offers protection against intracellularantigens or at cellular level

2) Not transferable through placenta

3) T lymphocytes and cytokines are the players

Cytokines that are communicators between leukocytes are Inter leukins ( IL) e. g. IL-1, IL-2



T Lymphocytes

1. Character istics of T lymphocytes

2. Surface receptor and Co-receptors of Tlymphocytes:

T C R + CD4 or T C R + CD83. Helper T cells (T H) C D4

4. Cytotoxic T cells (T C) CD8

5.

H I V targe

ts

ce

lls

with CD4c

o-rece

ptors



Antigen Recognition by T lymphocytes

Antigen can not be free-floating but needs to be presented to T lymphocytes along with M H Ccomplexes

M H C complexes are of Two types:

1. Class I : on surfaces of most nucleated cells of the body

2. Class I I: on surfaces of APCs such as Dendritic cells, B-cell, macrophages

Two possible ways of antigen presentation to Tlymphocytes: Ag+ M H C I or Ag+ M H C I I



1. Antigen presentation toT Lymphocytes: Ag+M H C I

Ag+M H C I complex will be presented by aninfected cell or an abnormal cell to aCD8+TCR containing T cell



Cytotoxic T Lymphocytes T C ( C T L )

a)Af ter recognition of an antigen,

two cel l types produced: effector (C T L) & memory cells

b)Function of C T L : destruction of target cellsvirus-infected cells, cancer cells, incompatible tissue

graftsc)When target cell is spotted, granules

with per for in are released by C T L

d)This

prote

in is

inse

rte

d into the

membrane of the offending cell,

to form a pore leading to death

of the target.



2. Antigen presentation toT Lymphocytes: Ag+ M H C I I

Ag+M H C II complex wil l be presented by an APC , antigen presenting cell, to C D4+T C R containing T cell



Helper T cells (T H)

a) A fter Ag recognition, differentiates into twotypes: effector & memory (therefore , 1 and2 responses here).

b) Functions: Helper T cells produce cytokines to influence the activity of

macrophages,

othe

r Tce

lls

andB cells: Overlap with humoral immunity

the adaptive immunity part 3-au 10-1.pdf

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