1.immunohaematology introduction to hematology.pptx

Introduction to hematology

1. Immunohematology U/s Amani Awad Ashmaig

2. Definition: known as blood banking it is a branch of hematology which studies antigen-antibody reaction and related blood disorder. Antigen Antigens are defined as substances recognized by the body as foreign, causing the body to produce an antibody to react specifically with it.

3. Characteristics of antigens: 1/Antigen must be Foreign; Autologous  antigens are  your own antigens (not foreign to you) Homologous, or allogenic , antigens are antigens from someone else that are foreign to you

4. 2/Antigen must be chemically complex. Proteins and polysaccharides are antigenic due to their complexity. lipids are antigenic only if coupled to protein or sugar.  3/Antigen must be large to stimulate antibody production.  Their molecular weight needs to be at least 10,000.

5. Factors determining whether an antigen will stimulate an antibody response: Degree of foreignness. Size and complexity. Dose of antigen administered

6. Antibodies: Proteins produced by lymphocytes as a result of stimulation by an antigen which can then interact specifically with that particular antigen.

7. Serum components: Human serum can be separated into albumin and globulin components Globulins can be separated into several different parts:  a. Alpha 1 and alpha 2 globulins b.  Beta globulins (serum complement) c. Gamma globulins ( immunoglobulins or antibodies)

8. structure of an antibody: Heavy chains  - made of alpha, gamma, delta, mu, or epsilon chains Light chains  - made of kappa or lambda chains Disulfide bonds  - hold chains together Hinge region  - allows antibody to flex to reach more antigen sites

9. 4. Fab fragments  - contains variable portion of antibody: antigen-binding sites 5. Fc fragment  - contains constant portion of antibody; also site of complement activation

10. Classes of antibodies: Immunoglobin G IgG Immunoglobin M IgM Immunoglobin A IgA Immunoglobin E IgE Immunoglobin D IgD

11. Differents between IgG and IgM antibodies: 1/ Size of the antibodies: IgG is small, it is comprised of only one immunoglobulin subunit (monomer). IgM is large, it is comprised of 5 immunoglobulin subunits.( pentamer ).

12. 2 /Number of antigen-binding sites: IgG has 2 binding sites IgM has 10 binding sites

13. 3/Serum concentration IgG is found in the largest concentration of all immunoglobulins in the plasma. IgM is found in relatively small amounts 4/Complement activation IgG = will do it if conditions are optimal IgM = very good complement activator

14. 5/Placental transfer IgG can cross placenta IgM and the other classes do not cross placenta 6/Optimum temperature of reactivity a. IgG = 37 o C ( worm antibody) b. IgM = less than 30 o C (cold antibody)

15. Antigen-Antibody Reaction: A reaction that occurs when an antigen combines with a corresponding antibody to produce an immune complex.

16. Stages of Ag- Ab reaction: 1/First stage  Sensitization: It is association of antibody with antigen lead to coated cells.

17. 2/Second stage  Agglutination: It is crosslinking of antibody between cells lead to clumped cells.

18. Converting of sensitization to agglutination: The distance between red cells is about 18 nm , IgM antibody can convert the sensitization to agglutination because the span between the Ag- Ab binding sites is 30 nm .  

19. But ,, IgG antibody can not because it has shorter span 15 nm so it need enhancers: Protease enzyme  reduce intercellular distance Albumin  act as polymer Antiglobuline  act as bridge between sensitized cells

20. Factors affecting the antigen-antibody reaction: 1/ Temperature: Cold Ab ( IgM ) bind best at low temperature 4 C , while worm Ab ( IgG ) bind best at body temperature 37 C .

21. 2/pH: reaction can occur when pH is between 5.5 _ 8.5 ( best at 7.0 ).   2/Ionic strength : Low ionic strength increase the rate of the reaction so low ionic strength solution (LISS) is used.