Activitation of B and T Cells by Antigen
- Remember innate vs. adaptive
- Remember anitgens have certain properties that allow them to be immunogenic. Such as: size, foreigness, polysaccharides
Cytokines
Properties
- MODULATE IMMUNE/ INFLAMMATORY RESPONSES (allow for balance)
- inc. small peptides and glycoproteins
- Made by variety of cell types including
- accessory cells
- leukocytes
- somatic cells
- short ½ life; one cell can make many different types of cytokines; as can many cells make the same cytokine
- ENDOCRINE, PARACRINE, AND AUTOCRINE
Classification
- Interferons (a,b,g)- interfered w/ viral replication
- Colony Stim. Factors- stimulate various elements of the bone marrow (shortens window of infection)
- Tumor Necrosis Factors- thought cure for cancer at first (TNF-b- lymphotoxin)
- Chemokines- chemotaxins to regulate immune response
- Interleukins- talk between WBCs; communication promotes immune response
- TH1® INF-g® CMI
- TH2® IL-4® B-cell growth factor
- IL-2 produced in both TH1&2 cells
Kinetics of an Immune Response
- Acute phase- IgM
- Convalescent phase- IgG
- In both primary and secondary responses the IgM titer is the same; the major difference is the IgG
- Remember IgG has a longer ½ life and can cross the placenta
- Primary Response
- latent period
- exponential phase
- steady state
- declining phase
Cellular Cooperation in the Immune Response
- Component cells include: Accessory cells, T cells, B cells
Accessory Cells (Antigen Presenting cells)
- involved in antigen degradation and epitope formation
- Include: monocytes/macrophages, dendritic, Langerhan’s, B cells (Memory response only)
Association with MHC
- APCs (Macrophage) INGEST Ag into phagosome which then binds with a lysosome where some proteolytic degradation occurs at this phagolysosome. All this time the MHC Class II molecules are being synthesized in the ER of the APC. The mature MHC Class II molecules then bind to the peptide fragments from the phagolysosomal vesicles and are transported to the surface of the APC for Antigen presentation.
- Remember the macrophage is NOT Ag specific but B and T cells are
Secondary (memory) Responses
- B and T cells act DIRECTLY
- there is no need for APC cells
- This is a helper T cell dependent Ab response
- ON TEST!!!!!!!!——- Il-1 = lymphocyte activating factor
- B-cell serves as APC and secretes IL-1
- The B cell (APC in this case) takes up the antigen and processes it along with MHC Class II molecules which, once at the surface of the B cell, allows for the T-Cell Epitope of the antigen to bind to the T cell Receptor/CD4. The IL-1 produced by the B cell and the antigen presentation has now activated the T cell which then releases its own interleukins (IL-2 and IL-4, IL-5). IL-2 is a T cell growth factor (autocrine) that further expands the T cell response. IL-4 and IL-5 are B cell growth factors that expands the response of the B cells (not the original B cell that was the APC) responsible for proliferation and differentiation and Ig synthesis as a secreting plasma cell that conveys the immunity.
Different Ag-Specific Responses
T dependent Antigens
- require helper T cell for B cell response
- need Hapten-Carrier complex
- requirements
1. B-cell priming
2. T-cell priming
3. secondary response
4. T-cell sensitization
5. Physical presence of hapten in conjugation w/ carrier molecule
T independent antigenic responses
- do not require helper T activity
- Antigens are large polymeric molecules like polysaccharides
- repeat sequences bind to many Ig receptors on the B cell (capping)
- ONLY an IgM response (No IgG response w/o T cells)
- NO Memory created
Tags: Accessory cells, antigenic responses, antigens, autocrine, B Cells, chemokines, Cytokines, endocrine, inflammatory responses, interferons, interleukins, kinetics, leukocytes, memory responses, paracrine, somatic cells, T cells, tumor necrosis
