The document summarizes key aspects of the immune system and immunoglobulins. It describes the immune system's mechanisms for recognizing self from non-self. There are five main classes of immunoglobulins - IgG, IgA, IgM, IgD, and IgE - which differ in structure, function, and location. IgG is the most abundant immunoglobulin and provides secondary immune response and antibody-mediated immunity. IgM is the first antibody produced during primary response and fixes complement. IgA provides mucosal immunity through secretions. IgD and IgE have uncertain functions but IgE mediates allergic reactions.

2.  Immune system:
It includes many mechanisms like phagocytic
actions of neutrophils ,monocytes and
macrophages.
SALIENT FEATURES OF IMMUNOLOGICAL
REACTION
 Recognition of self from nonself
 Specificity of the reactions
 Memory of the response

4. TERMS
ANTIGEN: Any substance which invokes an
immunological response.
ANTIBODY: substance produced by the host
against the antigen.
EPITOPE (antigenic determinant) : Binding
sites for antibody on antigen molecule.
Immune response is mediated by T&B cells
T cell: cell mediated immunity
B cell: humoral immunity
Plasma cells belonging to the B cells of
lymphocytes produce IMMUNOGLOBULINS
which is responsible for humoral immunity.

6.  Immunoglobulins are synthesised by B
cells(plama cells).
 Also called γ-globulins acting as
antibodies.
 Responsible for humoral immunity
STRUCTURE

8.  Y-shaped tetrapeptide
 Has two light chains(23 kd) and two heavy
chains (53-75 kd), joined by disulfide
bonds.
 Antigen binding occurs at both tips of Y.
 Hinge region: pepsin and papain cleaving
sites.
Constant region:3 quarters of H chain
(CH1,CH2,CH3) and half of L chain (CL);
amino acid compositon is constant .

9. VARIABLE REGION
 Consists VL and VH.
 Amino acid compositions are variable.
 Different in each person.
 Variable regions comprised of relatively
invariable regions and hyper variable
regions.
 Hyper variable region comprises of antigen
binding site, also called as Complementarity
Determinig regions (CDR’s).

12.  Papain (a proteolytic enzyme from papaya)
cleaves the Ig to produce two Fab (fraction
antibody) fractions and one Fc (fraction
crystallisable) .
 Pepsin cleaves Ig to produce F(ab)₂ where two
Fab are combined together.

14.  Five main classes based on type of heavy
chain make up.
 IgG, IgA, IgM, IgD, IgE.

16.  Most abundant (75-80%) in circulation.
 Y- shaped monomer.
 Major antibody of 2˚ immune response.
 Can cross placenta
 Main functions: opsonisation of bacteria,
fixes complements which enhances
bacterial killing, neutralizes bacterial toxins
and viruses.

17.  Normal serum concentration is 8-16 mg / ml
 Produce in secondary immune response
 Molecular weight is 150,000 and
sedimentation coefficient is 7S
 IgG has half life is 25 days
 The valency for antigen binding is 2

18.  Pentamer. Each subunit is joined by J
peptide.
 Can combine with 5 antigenic determinant
sites.
 Predominant Ig of primary immune
response.
 Fixes complement.
 Natural antibodies (ex: on RBC’s) are of IgM
class.
 Cannot cross Placenta
 Lyses blood borne bacteria

19.  It is the largest immunoglobulin.
 It has high molecular weight 950,000
 It is refferred to as macroglobulin
 The J chain holding the 5 subunits together at
the Fc region
 The serum level is very low .5- 2 mg/ ml
 The sediment coefficient of pentamer is 19S
 It is the earliest Ig to be synthesized by the
foetus

20.  It is the first Ab to appear in the primary
immune response , but it does not persist for
long time because of its short half life
 Maternal IgM does not cross the placenta but
human foetus can synthesize IgM
 IgM is useful indicator of intrauterine
infection such as congenital syphilis, rubella,
 Toxoplasmosis.
 Having multiple binding site ( 5-10 )

21.  Mono or dimer
 Secretory antibody seen mainly in
secretions of GIT, nasopharyngial tract,
urogenital tract,tears,saliva, sweat, milk and
colostrum.
 Prevents the attachment of bacteria and
viruses to mucous membranes.

22.  It has a molecular weight of 160,000
 The sedimentation coefficient is 7S
 Normal serum level is 0.6-4.2 mg/ml
 It has a half life of 6-8 days
 IgA plays an imp role in mucosal immunity
 IgA is found in mucous secretion ,tears ,saliva
 Colostrum ,GIT, prostate and respiratory
epithelium.
 It is found in small amount in blood

23.  Secretory IgA as termed as the mucosal paint
or antiseptic paint
 It is believed to inhibit the adherence of
microbes to the mucosa of the respiratory,
 GIT, urogenital tracts.
 IgA is also found to produce immunity
against tape worms.
 IgA present in colostrum.

24.  Monomer , found in low concentrations in the
circulation.
 Function is uncertain.
 Found on many B cells as well as in serum.
 May function as B-cell reeceptor.

25.  It is found in the blood serum as well as on
the surface of B cell.
 The serum level is 0.03 mg/ml
 Sedimentation coefficient is 7S
 The half life is 2-3 days
 IgD binds to basophils and mast cells and
activates them to secrete antimicrobial
factors.

26.  Ig is a monomer having a typical structure
 It has a molecular weight is 190,000
 It is a heat labile immunoglobin
 It is found only in trace amount
0.00004mg/ml
 The very low level of IgE synthesized by a
very few plasma cell of the body
 But in person with allergic its level may be 50
– 100 times higher

27.  Monomer, found in low conc. In serum but
elevated in allergies.
 Mediate allergy, hypersensitivity, and
anaphylaxis.
 IgE stimulates mast cells and basophills to
release Histamine and other anaphylactic
substances which brings about inflammation,
vasodilation , hypotension and bronchial
constriction.

28.  The main function of IgE is to provide
immunity against helminth worms.
 It also provide immunity against protozoan
parasites
 IgE antigen interaction on mast cells results
in degranulation of the mast cells with release
of vasoactive amines.
 IgE mediate reaginic hypersensitivitry

29. TO BE
CONTINUED……
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