Bone marrow Stem cell Immature lymphocytes Via blood Antigen receptors Thymus T cell B cell Via blood Final maturation of B and T cells in a lymphatic organ Lymph nodes, spleen, and other lymphatic organs Humoral immune response Cell-mediated immune response Key Point to Remember: Each B and T cell displays unique set of antigen receptors on cell surface Each receptor can specifically bind to a unique antigen
1 Primary immune response B cells with different antigen receptors Antigen receptor on the cell surface CLONAL SELECTION Every B cell displays unique antigen receptor on surface
1 2 Primary immune response B cells with different antigen receptors Antigen receptor on the cell surface Antigen molecules CLONAL SELECTION Antigen only binds to B cell with complementary receptor
1 2 3 Primary immune response B cells with different antigen receptors Antigen receptor on the cell surface Antigen molecules First exposure to the antigen CLONAL SELECTION The selected B cell now divides rapidly!!! I WON THE ANTIGEN LOTTERY!!
Figure 24.7A_s4 1 2 3 45 Primary immune response B cells with different antigen receptors Antigen receptor on the cell surface Antigen molecules First exposure to the antigen Antibody molecules Plasma cells - secrete antibodies Memory cells Well mark the Pathogen for Elimination!! Well hang out And wait for the next invasion
Figure 24.7A_s5 Memory cells Second exposure to the same antigen Antigen molecules Alright boys, the pathogen is Back!! Looks like were in Charge of the second offensive - Get ready to divide!! Secondary immune response
Memory cells divide Secondary immune response Antibody molecules Memory cells Plasma cells Looks like we are off to fight This pathogen again! But now we can respond Faster with a larger army - those Bugs wont know what hit them!
Time (days) 56 49 4235 2821 14 7 0 Antibody concentration Antibodies to X Antibodies to Y Second exposure to antigen X, first exposure to antigen Y First exposure to antigen X Primary immune response to antigen X Secondary immune response to antigen X Primary immune response to antigen Y 2nd response occurs quicker with greater magnitude!!
Figure 24.8B Antigen Light chain Heavy chain Antigen-binding sites C C C C V V V V Antigen-binding site VARIES between each unique antibody The CONSTANT region defines Ab class and effector action V = variable C = constant
Bacterium Virus Neutralization (blocks viral binding sites; coats bacteria) Binding of antibodies to antigens inactivates antigens by Agglutination of microbes Precipitation of dissolved antigens Activation of the complement system Bacteria Antigen molecules Complement molecule Foreign cell Hole Leads to Cell lysis Enhances Phagocytosis Macrophage Animation: Antibodies Antibodies mark antigens for elimination
Figure 24.UN01 The humoral immune response: B cell T cell makes which bind to AntibodiesAntigens in body fluid The cell-mediated immune response: Infected body cell Self-nonself complex
Antigen from the microbe (nonself molecule) Antigen-presenting cell Self protein Microbe Macrophage 1234567 Self-nonself complex Phagocytic cell (yellow) engulfing a foreign cell T cell receptor Helper T cell Binding site for the antigen Binding site for the self protein Interleukin-2 stimulates cell division B cell Cytotoxic T cell Interleukin-2 activates B cells and other T cells Cell-mediated immune response (attack on infected cells) Humoral immune response (secretion of antibodies by plasma cells) Infected body cells will display antigens of pathogen on cell surface Helper T cells are trained to recognize foreign antigens and alert B cells and Cytotoxic T cells