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CHAPTER 21

~IMMUNITY~

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21.1 IMMUNE RESPONSE# Immunity

# Classes of antibody

# Humoral and cell mediatedimmune response

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21.1 IMMUNE RESPONSE# Roles of lymphoid organs

# Antigen-antibodyinteractions

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At the end of this topic, students should be able to:-

State the roles of lymphoid organs in immunity

such as:-

1) Thymus

2) Spleen

3) Tonsil

4) Lymph nodes5) Bone marrow

State the various types of antigen and antibody

interactions

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ROLES OF LYMPHOID

ORGANS

1) Thymus

Site where thelymphocytecells mature.

Secretethymosine.

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2) Spleen Contains

lymphocytes and

macrophages. Functions to

remove bacteria

and worn-out redblood cells.

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3) Lymph Nodes

Contain

lymphocytesandmacrophages.

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4) Bone marrow

Site of origin

of all types ofblood cells.

White bloodcells functionin immunity.

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5) Tonsil

Areas oflymphoidtissue oneither side of

the throat.

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ANTIGEN

Any foreign

molecule that elicits

an immune

response by bindingto receptors of B

cells or T cells.

Usually protein,glycoprotein or

polysaccharide.

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All cells posses antigen in their cell

surface membranes:

acts as markers

enables cells to recognize each other

Own antigen self

Foreign antigen non-self

ANTIGEN

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Epitope a small, accessible region of an antigen

to which an antigen receptor or

antibody binds an antigen may have several different

epitopes

each epitope is recognized by a

different antibody

ANTIGEN

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ANTIGEN

Different antibodiescan recognize

distinct epitopes on

the same antigen.Antibodies can

recognize free

antigens as well as

antigens on a

pathogens surface.

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TYPES OF ANTIGEN-

ANTIBODY INTERACTIONS

AGGLUTINATIONAGGLUTINATION

NEUTRALIZATIONNEUTRALIZATION

PRECIPITATIONPRECIPITATION

ACTIVATIONACTIVATIONCOMPLEMENTCOMPLEMENT

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1. AGGLUTINATION

Clumps of

bacteria being

held together &

easier for

phagocytes to

engulf.

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2. NEUTRALIZATION Antibodies bound

to antigen on the

surface of virus.

Neutralize it by

blocking its ablity

to bind to a hostcell.

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3. PRECIPITATION

Cross-linking of

soluble antigen

molecules &

immobile precipitates

are easily engulfed byphagocytes.

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4. ACTIVATION COMPLEMENT

CCombine with complement proteinswhich produce lesions in membrane

that result in cell lysis.

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1)There are five lymphoid organs involved

in immunity : thymus, spleen, tonsil,

lymph nodes, and bone marrow.2)There are four types of antigen-antibody

interactions : agglutination,

neutralization, precipitation, andactivation complement.

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21.1 DEVELOPMENT OF IMMUNITY# Primary and secondary

immune response

# Concept of self and non-self