Department of Microbiology IMMUNE RESPONSE Dr. Mohit Bhatia Assistant Professor Department of Microbiology AIIMS, Rishikesh

LAYOUT INTRODUCTION ANTIGEN PRESENTATION CELL MEDIATED IMMUNE RESPONSE HUMORAL IMMUNE RESPONSE AN OVERVIEW OF CYTOKINES

INTRODUCTION Immune response refers to highly coordinated reaction of the cells of immune system and their products Cell mediated immune response: T cells Humoral immune response: Antibodies NK cells, macrophages, granulocytes are also component of CMI (Non-specific)

ANTIGEN PRESENTATION

ANTIGEN PRESENTING CELLS

DIFFERENCES BETWEEN DIFFERENT APCs

PATHWAYS OF ANTIGEN PRESENTATION

ENDOGENOUS (MHC I) EXOGENOUS (MHC II) Talk about receptor mediated endocytosis and autophagy.

CELL MEDIATED IMMUNE RESPONSE Talk about Groups I & II CMI.

Development of αβ T cells

Positive & Negative selection of thymocytes results in mature T cells that are both self-MHC restricted & self-tolerant

INSTRUCTIVE & STOCHASTIC MODELS

T CELL RECEPTOR-CORECEPTOR COMPLEX & OTHER SURFACE MOLECULES

INTERACTIONS BETWEEN T CELLS & APCs

OVERVIEW OF TCR MEDIATED SIGNALING

TH-cell activation requires a co-stimulatory signal provided by APCs

CONCEPT OF CLONAL ANERGY

Super-antigen mediated cross-linkage of T-cell receptor and class II MHC molecules TSST-1 EXFT SPE- A,B,C,D

Activation of TH cells by signal 1 & co-stimulatory signal 2 up-regulates expression of IL-2 and the high affinity IL-2 receptor, leading to the entry of the T cell into the cell cycle and several rounds of proliferation. Some of the cells differentiate into effector cells, others into memory cells.

FEATURES OF NAÏVE & EFFECTOR T CELLS

EFFECTOR MOLECULES PRODUCED BY EFFECTOR T CELLS

GENERATION OF EFFECTOR CTLs

STAGES IN CTL MEDIATED KILLING OF TARGET CELLS

CTL MEDIATED PORE FORMATION IN THE TARGET CELL MEMBRANE

PATHWAYS OF TARGET CELL APOPTOSIS STIMULATED BY CTLs

ASSESMENT OF CMI Mixed lymphocyte reaction Cell mediated lympholysis Graft versus host reaction

NK CELL MEDIATED KILLING: OPPOSING SIGNALS MODEL

Antibody-Dependent Cell-Mediated Cytotoxicity(ADCC)

ANTIBODY DEPENDENT CELL MEDIATED CYTOTOXICITY (ADCC)

HUMORAL IMMUNE RESPONSE

OVERVIEW OF B CELL DEVELOPMENT

Pro-B CELL & BONE MARROW STROMAL CELL INTERACTION

B-CELL RECEPTOR-CORECEPTOR COMPLEX

THYMUS INDEPENDENT & DEPENDENT ANTIGENS

PROPERTIES OF TI & TD ANTIGENS

B-CELL MEDIATED IMMUNE RESPONSE

B-CELL MEDIATED RESPONSE

Schematic diagram of a peripheral lymph node showing anatomic sites at which various steps in B-cell activation, proliferation and differentiation occur. The cortex is rich in B cells & the paracortex in T cells. Both B and T cells are present in large numbers in the medulla. A secondary follicle contains the follicular mantle and a germinal center.

OVERVIEW OF CELLULAR EVENTS WITHIN GERMINAL CENTERS

The interactions of numerous cytokines with B cells generate signals required for proliferation and class switching during the differentiation of B cells into plasma cells

NAÏVE & MEMORY B CELLS

PRIMARY & SECONDARY IMMUNE RESPONSE

COMPARISON OF PRIMARY & SECONDARY IMMUNE RESPONSES

EFFECTOR FUNCTIONS OF HUMORAL IMMUNITY

Phagocytosis of antibody-antigen Neutralization Bacterial toxins Host cell Toxin receptors Neutralization by antibody Phagocytosis of antibody-antigen complex by macrophage Fc receptor Forming phagosome

Opsonization Extracellular bacteria Opsonization Macrophage Ingestion by macrophage Digestion in lysosome

Complement Activation Digestion in lysosome Bacteria in plasma Complement activation Lysis and ingestion

TRANSCYTOSIS

AN OVERVIEW OF CYTOKINES

INDUCTION & FUNCTION OF CYTOKINES

ATTRIBUTES OF CYTOKINES

Interaction of antigen with macrophages and the subsequent activation of resting TH cells leads to release of numerous cytokines (blue arrows), generating a complex network of interacting cells in the immune response.

SUMMARY OF CYTOKINES Talk about therapeutic uses of cytokines as well.