Chapter 22, part 3
The Lymphatic System and Immunity
SECTION 22-4 Specific Defenses
Forms of immunity
Innate immunity
Genetically determined
Present at birth
Acquired immunity
Not present at birth
Achieved by exposure to antigen
Active immunity
Passive immunity
Figure 22.14 Types of Immunity
Properties of immunity
Specificity – activated by and responds to a specific antigen
Versatility – is ready to confront any antigen at any time
Memory – "remembers" any antigen it has encountered
Tolerance – responds to foreign substances but ignores normal tissues
The immune system response
Antigen triggers an immune response
Activates T cells and B cells
T cells are activated after phagocytes exposed to antigen
T cells attack the antigen and stimulate B cells
Activated B cells mature and produce antibody
Antibody attacks antigen
Figure 22.15 An Overview of the Immune Response
SECTION 22-5 T cells and Cell-mediated Immunity
Major types of T cells
Cytotoxic T cells (TC) – attack foreign cells
Helper T cells (TH) – activate other T cells and B cells
Suppressor T cells (TS) – inhibit the activation of T and B cells
Antigen presentation
Antigen-glycoprotein combination appears on a cell membrane
Called MHC proteins (Major Histocompatibility Complex)
Coded for by genes of the MHC
T-cells sensitive to the antigen are activated upon contact
MHC classes
Class I – found on all nucleated cells
Class II – found on antigen presenting cells and lymphocytes
Lymphocytes respond to antigens bound to either class I or class II MHC proteins
Antigen recognition
T cell membranes contain CD markers
CD3 markers present on all T cells
CD8 markers on cytotoxic and suppressor T cells
CD4 markers on helper T cells
Figure 22.16 Antigens and MHC Proteins
Figure 22.16 Antigens and MHC Proteins
Figure 22.16 Antigens and MHC Proteins
Activation of CD8 cells
Responds quickly giving rise to other T cells
Cytotoxic T cells – seek out and destroy abnormal cells
lymphotoxin
Memory TC cells – function during a second exposure to antigen
Suppressor T cells – suppress the immune response
Figure 22.17 Antigen Recognition and the Activation of Cytotoxic T Cells
Figure 22.17 Antigen Recognition and the Activation of Cytotoxic T Cells
Activation of CD4 T cells by antigens presented on class II MHC proteins
Produces helper T cells and memory T cells
Activated helper T cells
Secrete lymphokines that coordinate specific and nonspecific defenses
Enhance nonspecific defenses
Stimulate the activity of NK cells
Promote activation of B cells
Figure 22.18 Antigen Recognition and Activation of Helper T cells
Figure 22.19 A Summary of the Pathways of T Cell Activation
