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 -