Adaptive immune system• Four characteristics _diversity-in recognizing structure of antigens

– Antigenic Specificity – ability to recognize and respond to particular targets.

– Memory – second exposure to the same organism produces a larger and more rapid response than occurred at the primary exposure.

– Self/non self recognition

TYPES OF IMMUNITY

ACTIVE IMMUNITY

• EXPOSURE TO ANTIGEN

• IMMUNITY ACHIEVED BY INJECTING ANTIGENS

• ACTIVATION OF IMMUNE SYSTEM

• IMMUNE STATE DEVELOPS OVER A PERIOD OF WEEKS

• IMMUNOLOGICAL MEMORY DEVELOPS

PASSIVE IMMUNITY

• NO EXPOSURE TO ANTIGEN

• IMMUNITY ACHIEVED BY INJECTING Ab or Ag REACTIVE T CELLS

• NO IMMUNE SYSTEM ACTIVATION

• IMMUNITY DEVELOPS IMMEDIATELY

• NO IMMUNOLOGICAL MEMORY DEVELOPS

cells

T -lymphocytes

Effector T cells

Activated T helper cells

Cytotoxic T lymphocytes

Memory T cells

B lymphocytes

Memory B cells

Plasma cellsAntigen

presenting cells

a) B lymphocytes• Mature within bone marrow• B cells receptor is a membrane bound

antibody molecules.• Can recognize antigen alone• Two types-Memory B cell- longer life span -same membrane bound antibody as their parent B cellsPlasma cells-secretes antibodies

b) Antigen presenting cells

• They express class ll MHC molecule on their membrane.

• They are to deliver a single that is necessary for T helper cell activation

c) T lymphocytes• Formation and maturation• Recognizes only antigen bound to cell

membrane proteins called major histocompatibility complex (MHC)

• Two type of MHC molecule-Class l MHC-expressed by all

nucleated cells of vertebrates speciesClass ll MHC- expressed by only

antigen presenting cells

Helper T lymphocyte• Have CD4 glycoproteins on their surface.

• Interact with MHC class ll molecules

• Secretes many growth factors, cytokines, interleukin

• Activate s macrophages, B cells, Tc cells and other cell

Activation of T cells: Helper

Activated helper T cell

Monokines

MHC Class II

T cell receptor

Antigen-presenting cell

CD4 protein

Antigenic peptide

Antigen is processed

Resting helper T cell

Class II MHC

Lymphokines

Helper T cell receptor recognizes processed antigen plus Class II MHC

Macrophage

Processed antigen and Class II MHC are displayedAntigen

Helper T cell

T cytotoxic cells

• Also known as killer T cells. Have CD8 glycoprotein

• Stimulated by cytokines released by T helper cells

• Recognizes antigen MHC class l molecules complex

• Differentiates into cytotoxic T lymphocytes

• No cytokine secretion

• Exhibits cell killing activity for altered self cells-tumor cells & virus infected cells

Antigen receptors

Killer cell

Infected cellAntigen-presenting cell Antigen-presenting cell

CD8 protein

Cell membrane MHC

Class IMHC Class I

Antigenic peptide

T cell receptorCD4

proteinCell membrane MHC

Class II

Antigenic peptide

T cell receptor

Cell membrane

Antigen

Antigen-specific receptor

Helper T cellB cell

Types of immune response

Acquired immune response

Cell mediated response T lymphocytes

Humoral response B lymphocytes

THANK YOU