Lecture-17 humoral and cell mediated immunity.pptx

The immune cells involved in adaptive immunity is deciphered. Steps of humoral immune response including complement mediated bacterial cell lysis are shown

1. Lecture -17 Humoral/CM immunity Prof. Sreerama Krupanidhi Email: [email protected] 9/5/2024 Prof. Sreerama Krupanidhi 1

2. Focus To understand acquired or adaptive immunity. To acquaint with Steps of humoral immune response. To trace Steps of cellular immune response. 9/5/2024 Prof. Sreerama Krupanidhi 2

3. Learning outcomes The immune cells involved in adaptive immunity will be known. Steps of humoral immune response including complement mediated bacterial cell lysis will be known. 9/5/2024 Prof. Sreerama Krupanidhi 3

4. Cell mediated immunity: killing a virus infected cell 9/5/2024 Prof. Sreerama Krupanidhi 4

5. Definition of acquired/adaptive immunity Adaptive immunity is body's ability to eradicate possibly harmful foreign materials or abnormal cells by developing specific immune response against a particular antigen . Acquired immunity has two components: humoral immunity and cellular immunity. Humoral immunity is mediated by B Lymphocytes Cellular immunity is mediated by T lymphocytes 9/5/2024 Prof. Sreerama Krupanidhi 5

6. MHC Antigens: Major Histocompatibility Complex / HLA Ag (Human Leukocytes Associated Ag) MHCs (HLAs) are transmembrane glycoproteins of human leukocytes. These transmembrane glycoproteins are encoded by Histocompatibility Genes present on the short arm of chromosome 6 They are designated as the self antigens, which are very specific to a person and present on the surface of ce ll membranes of all the nucleated cells of body EXCEPT RBCs . Class I Class II On all nucleated cell Predominantly On APC 9/5/2024 Prof. Sreerama Krupanidhi 6

7. Contribution of MHCs and TCRs in CMI Cytotoxic T-cells express CD8 along with the T-cell receptor (TCR). CD8 facilitates the binding of MHC-I coupled with antigenic peptide to the T cell receptor. T-helper cells express CD4 which facilitates the binding of MHC-II coupled with bacterial antigenic peptide to the helper T cells receptor. 9/5/2024 Prof. Sreerama Krupanidhi 7

8. Distinction between HI and CMI Humoral Immunity It is a ‘B cells’ generated - antibody mediated immune response especially effective against bacterial antigens found in the serum. Cellular Immunity It is a ‘T cells’ mediated immune response especially effective against intracellular organisms like viruses, parasites, fungi and others like cancer cells and transplant cells (few bacterial infection like tubercular bacilli). 9/5/2024 Prof. Sreerama Krupanidhi 8

9. Ag processing and presentation to Th cell Phagocytosis of Ag by APC Proteolytic degradation of Ag in the cytosol of APC Presentation of the processed Ag (epitopes) coupling with MHC II to TCR complex of Helper T cells ( T H 2 ) or CD4 cells. Th cell is primed and communicate to the B-cell. 9/5/2024 Prof. Sreerama Krupanidhi 9

10. Humoral immunity: Plasma cells and Igs Clones of B cells recognize antigens (Clonal Selection) through the T H 2, Gets activated by the released cytokines Differentiate into plasma cells and memory cells → The immunoglobulins are baled out and they are with: 2 identical heavy chains : Each has a constant and a variable region 2 identical light chains : Each light chain has a constant and a variable region Fab – fragment antigen binding site Fc- Fragment constant and some immune cell binding site 9/5/2024 Prof. Sreerama Krupanidhi 10

11. HI :: Neutralization of Ag by IgGs Tailored IgGs released into the blood stream will bind to the antigens that they are specific for. 9/5/2024 Prof. Sreerama Krupanidhi 11

12. Complement system: an arm of HI 9/5/2024 Prof. Sreerama Krupanidhi 12 Cell Lysis Perforin molecule Immune complex

13. HI: The release of Ab upon priming with Ag 9/5/2024 Prof. Sreerama Krupanidhi 13

14. Summary The acquired immunity comprising of the two components namely Humoral immunity and Cell mediated immunity are understood. The MHC class I and II transmembrane molecules coupled with viral and bacterial antigens respectively primed the Tc and Th2 cells to elicit immune response. The complement system is dormant and gets activated with the onset of immune-complexes. The baling out of antibodies from the B cell upon first and second priming reveals the intensity of the elicitation of immune response. 9/5/2024 Prof. Sreerama Krupanidhi 14

15. Self assessment Distinguish between the MHC class I and II. How does HI differ from CMI? What is plasma cell? How is it derived? What is its function? What is the role of APC? 9/5/2024 Prof. Sreerama Krupanidhi 15

16. Acknowledgements We acknowledge online resources/public domains for the use of the content to develop teaching material and to disseminate the knowledge . 9/5/2024 Prof.Sreeraama Krupanidhi 16

17. Thank you 9/5/2024 17 Prof. Sreerama Krupanidhi