primary &secoundary immune respons

Primary and Secondary Immune Response
Dr.Baha,Hamdi.AL-Amiedie
Ph.D.Microbiology
Primary Immune Response:
Primary Immune Response to initial antigenic stimulus is slow, sluggish, short live with a long lage phase and low antibody titer
that do not persist for along time ,antibody formed are 1gM. When tetans toxoid is given to host an immune response is mounted .The response could be detected intervally by collection blood and estmaton of antbody
titers, it was found that the immune response follows the time curve in which the first day after Antigen injection 10-12 days after the first injection antibody begin to rise in their titer, this stage is known phase of antibody rise. After this stage any blood sample will take the same antibody titer this called platue phase. Within the third 3 week or more the antibody titer in the collection the sample begin to decline , this stage
is called decline phase . The antibody classes start with 1gM followed by IgG and described as Antigen specific response.
Secondary Immune Response:
Secondary Immune Response to subsequent stimuli is prompt, powerful prolonged and with much higher level of antibody it vast for long time,
Antibody predominatly formed are IgG, when boostinge of toxoid is given to the same host the lage phase is reduced. and the antibody rise phase is begin faster than first phase within a week, prescence of memory cell which are specific for antigen, so always if we give multiple dose of the same Antigen to the same host will lead good immune response because of the regulatory mechanisum , within the body for the amount of antibody against Antigen ,The antigen type is in these responses is B-dependent-Antigen .The time carve is follow factor influencing Antibody production:
1. Age
2. Nutritional status
3. Route of administration
4. Size and Number of doses
5. Multiple antigens
6. Adjuvant
7. Immunosuppressive agent
Cellular Immune Response: -
The term cell rnediated immunity refers to the specific immune responses that do not involve antibodies, induction of cell mediated immune response (CMI) consists of specifically sensitizing T-lymphocytes comes against the antigen. When sensitized T-cell comes in contact with antigen determinant (epitopes)by the function of Antigen Presenting Cell (APC) ,so T-cell under goes blast transformation and clonal proliferations selectively in paracortical areas of lymph nodes.
lymphokines: material required as secreted proteins from the activated T-cell , These Lymphokine have several biological function
1-Effect on macrophage : This Lymphokine is function is covered out
by the following:
a-Macrophage inhibition Factor (MIF)
b-Macrophage aggregation Factor (MAF)
c-Macrophage chemotactic Factor (MCF)
2-Effect on Lymphocytes:This role is done by:
a-Blastogenic factor (BF)
b-Potentiation factor (PF)
c-Cell co-operation factor (CE).
3-Effect on granulocyte: •.
a-Inhibition factor (IF)
b-Chemotactic factor(CF)
4-Effect on tissue cultur:
a-Lymphotoxin
b-Proliferation inhibition factor (PIF)
c-Interferon
Table- 1 Interleukines
Immunoglobuline
Or Antibodies
Are glyeoproteins present in the gama- globuline fraction of serum. Immunoglobuline generally natural present in blood without previous antigenic stimulation However antdody are the Immunoglobuline that
Produce specifically by B-cell after antigenic stmulaton . Thus all antibodies are Immunoglobuline while no all Immunoglobuline are antibody
The charateriste of antibody are
1. glycoprotein in nature.
2. specific to antigine induce them.
3. React specifically with their own antigen
Antibody are distributed in serum, body fluid, Urine ,Saliva , Ear wax and tears.
The anitbody molecule are found to be of dfferent classes , the classification depend on :
1-The molecular size
2-Natur of carbohydrate,
3-Amino acid sequnence.
The classes of Antibodiess are IgM, IgG, IgE & IgD.
The dfference between these Classes depend on the type of heavy chain in each molecule, Immunoglobulines mak 20- 25 % of total serum protein, the terum lmmunoglobuline is structural & chemical concept while antibody is biological and function concept.



The basic structure of antibody Molecule
the antibody molecule is a four chains molecule which are:
1- two light chain (I.C) consist of 214 amino acid, 106 amino acid respect the constant region of molecule while variable region consist of 108 amino acid for Kappa & Lambda
2- two heavy chain (HC) consist of 440 amino acid, residcus 322 amino acid occur in constant region (CH). 118 amino acid in
the variable region (VH)
There are 5 Classes of (HC) Heavy chain content for five Classes of lmmunoglobulines:
1-(Gamma) or lgG
2-(Mu) or lgM
3-(Alpha) or lgA
4-(Epsilon) or lgE
5-(Dalta) or IgD
The variable region in both heavy chain (HC) and light chain (LC) are consist the antigen combination sit.
Fab : it is amino acid terminal half of heavy chain & light, it act as Antigen binding fragment .

Fc: It is carboxyl terminal half of heavy chain & determine biological properties of Immunoglobuline







Antigen and Antibody Reaction

Antigen-Antibody reactions are useful in Laboratory diagnosis of various diseases and in the identification of infectious agents in epidemiolo
gical survey. Antigen - antibody reactions in vitro are called serological reactions.
The following arc the important tests based on
antigen -Antibody reactions
• Agglutination
• Precipitation
• Redial — immunoassay
• ELISA
• Immune fluorescence
• Neutralization
• Haemegglutination
• Antiglobuline test ( comb’s test )
• Complement fixation test. and other tests using complement system

The antigen -Anti body complex is not. found firmly together and may dissociate spontaneously unless PH, salt concentration and temperature are properly adjusted the major forces that hold antigen - antibody complex together are their ionic attractions the antigen have three type which affected the Raction Antigen —Antibody a-movement antigen b- Bivalent Antigens, c-multivalent. Antigens
Precipitation:
when soluble antigen combines with its antibody in presence of electrolytes (Nacl) at suitable temperature and PH the antigen — antibody complex forms insoluble Precipitate.


Lattic hypothesis: is multivalent antigens combine with bivalent antibody in varying proportions , depending antigen antibody ratio in reaction mixture Precipitation results.
When large lattice is formed consisting of alternating antigen and antibody molecules.
This possible only in the zone of equivalence. zone of antigen and antibody excess lattic does not enlarge as valiancy of antigen and antibody is fully satisfied .
In general precipitation is maximum when optimal proportions of
antibody combine precipitation can, be produced in solutions or in semisolid (agar gel) medium, precipitation in solution can be shown by adding these two on a slide and mixing well or in small narrow tubes one -













The Complement system
A plasma protein with 25 fraction these protein heat sensitive at 56 C for 30 minutes , the chemical structure of complement is polypeptide chains interconverted by disulfide bound.
The complement system plays a major role in host defense and the inflammatory process. The complement component synthesized in liver , spleen as well as enterocytes with 25 fractions. Nine fraction of which are involve in complement pathways which act as sequential manner and can be activated or inhibited , properdin is important on first exposure to Microorganism (first Immune Response)
Complement classical pathway in second exposure to microorganisum (second immune response) complement defect associated with disease condition, Activators of complement system are of two types immunological &non-.immunology ,also complement system regulated with inhibition factors.
The function of complement system:
The complement displays a wide range of biologial activites when activated:
1-Mediated Antigen-Antibody Reaction
2-Mediated inflammatory response
3-Facilitate phagocytosis.
4-Facilitate blood coagulation
5-Neutralize viruses effect & the effect of bacterial LPS
6-Play a role in the non-specific resistance to microbial infection
7-Associated with immune distraction - of blood cellular component
Classical complement system pathway:
The activation of this is
1) Antigen -Antibody.
2) Non - Immunological such as C-Reactive protein and pIy]ococus
aureus protein A.
































Alternative (properdine) Complement system pathway
1.The immunological activator lgG, IgA molecules
2. Non - Immunological Activator,
a. Lipopoly saccharide.
b. Copra, Venum factor.
The Mechanism of cell lysis with complement when fraction of complement system binding with the cell surface of cell. in present of’ antigen & Antibody it will non - equilibrium in permeability of cell wall non - equilibrium in protein synthesis process of hole in cells.
Non - equilibrium in metabolic of cells presence of hole in cell
wall and that will lead to lysis of cells
Complement fixation test : This is very sensitive is very
sensitive test and is capable of detection Antigen & Antibody it is used
for serological diagnosis with principle : The ability of Antigen – Antibody
complex to fix complement used for diagnosis of disease
1. Spirochaetal disease e.g Sphilis (wasserman reaction)
2. Rickettsial disease e.g typhus fever.
3. Viral disease like lymphogranuloma venerum
4. Parasitic disease e.g kala-azar, hydatid cyst, amoebiasis