MMI133 Lecture Notes - Lecture 16: Immunoglobulin G, Cytotoxicity, Antigen
Specifically generated host defenses (e.g. defense for SCID, AIDS)
Innate Immunity = nonspecific responses
(skin, flora, complement, inflammation, phagocytosis
Adaptive Immunity - specific response
, specialized immune cells, self/nonself recognition and
memory cell generation, specifically based on antigen recognition.
Antigen - foreign molecule that is recognized by immune cells and elicit immune response, most
immunogenic antigens are proteins.
Antibody - protein produced by B cell that recognizes a specific epitope on an antigen.
*Antibody A - recognition & Antibody B - no recognition
Stem Cell
| |
Lymphoid Cells Myeloid Progenitor (Granulocytes)
Specific Defense
● takes 5-7 days to develop
● delayed response
● highly diverse + specific
● generates memory (why vaccines work)
● Mediated by B lymphocytes (humoral/body fluid) & T lymphocytes (cell mediated)
Innate
Adaptive
● antigen independent
● immediate response
● not antigen specific
● no memory
● antigen dependent
● lag time responses
● antigen specific
● memory
B Lymphocytes
● produces antibodies in response to specific antigens
●produces cytokines, chemicals that alter cell behaviour through signals
●act as an antigen presenting cell (APC’s) to activate other immune cells to combat infection
●produced in the bone marrow (is antigen independent through production
)
●Activation - activated in peripheral lymphoid organs/gland and is antigen dependent
●Differentiation - plasma cells or memory B cells
, produced in peripheral lymphoid organs
and is antigen dependent
● Most effective against extracellular antigens
1. Antigen recognized by IgM
once antigen binds
2. B cell is then activated
3. Rapid cell division occurs (Proliferation/ Clonal Expansion)
. All proliferating cells have
B cell receptors (BCR) and specificity for antigen.
4. Memory Cells are created, or Plasma/Effector Cells.
Memory cells on 2nd encounter
will be activated at a faster rate and can contribute to plasma/effector cells.
5. Antibodies are secreted into the bloodstream
B Cell Activation
● depends on the antigen
●Thymus-dependent antigens are proteins
require a helper T cell (TD)
●Thymus-independent antigens are made from other molecules
(TI)
Cytokines
●soluble protein secreted by immune cells
● cause B cell proliferation (clonal expansion) and class switching
Class Switching
●changing the Ig produced by the B cell with no loss of antigen specific (e.g. Igm to IgG)
● produces different antibodies depending on environment surrounding cell
Basic Antibody Structure
Fab Region
● variable region
● antigen binding sites
● different combination of all the variable regions gives rise to a large repertoire of different
antigen specificity
FC Stem Region
● constant region
● recognized by other immune cells with FC receptors (binding site)