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immunity due to parasites.pdf

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					Cells of adaptive immune
          system
     Lymphocytes
Humoral Immune Response
                        B Cells

Mature in the BM.

Mature B cells have antibodies (Ab) on their surface
( 1.5x105 molecules/cells).


All antibodies on a single B cell have identical binding sites
for antigen (Ag).

B cells express CD45
B cells also express MHCII  functions as
antigen presenting cell (APC).
                                B Cells


                                Naive B cell

                                    Ag Exposure


              Memory Cells                        Plasma Cells


Remain in BM until secondary Ag encounter         Secrete Ab
           Immunoglobulin
Immunoglobulins functions as antibodies that bind
antigen
Immunoglobulins (Ig) found in serum

Opsonization: the process by which opsonins increase
phagocytosis of particulate antigens
Immunoglobulin
                 Immunoglobulin
Immunoglubulins consist of two
Fab-like fragments F(ab)2 and
one Fc fragment.

F(ab)2 = Region for antigen binding

polypeptide chains:
2 heavy chains
and
2 light chains



CDR=
complementarity determining regions
                         IgA
10-15% of Ig in serum

Predominant Ig in external secretions such as milk,
saliva, tears, mucus of bronchial, genitourinary and
digestive tracts.

In serum IgA = Monomer

IgA of external secretion called secretory IgA is dimer


 IgA serves an important effector function at mucous
 membranes (main entry sites for pathogens)
                        IgG
Most abundant in serum (80%)

Monomer

Four IgG subclasses IgG 1-4

IgG1, 3 and 4 = Cross the placenta and protect developing
foetus

IgG activates complement system

IgG = Opsonins by binding Fc receptors on phagocytic
cells
                         IgM

5-10% of total serum immunoglobulins

Monomeric IgM is membrane-bound antibody

Secreted IgM is pentamer (I.e. five monomeric subunits
held together by disulphide bonds)


First Ig produced in response to an antigen

First Ig synthesized by neonates
                        IgE
Very low serum concentration


Mediate hypersensitivity reactions responsible for hay
fever, asthma and anaphylactic shock


IgE binds to Fc receptors on membranes of basophils and
mast cells


Cross linking of IgE molecules by         allergens   
degranulates basophils and mast cells
                      IgD

0.2% of total Ig


Unknown function


Membrane-bound Ig


Expressed on mature B cells

				
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Description: immunity due to parasites.pdf