Basic concepts Flashcards
Timeline of immune response
Response changes drastically over time!!
- over course of infection
- over lifetime
Recognition -> decision making -> effector
Waves of response, amplification
Overview of defense systems
Physical barriers
Innate immunity (broadly reactive, non-specific)
Adaptive immunity
Antigen
Anything that reacts with antibody
Should be foreign or non-self protein, pathogenic vs normal microbiome
Immunogen
Anything that produces immune response
not necessarily “antigen”
Immunologic memory
Specific response to previously encountered antigen
Produces secondary response that is more rapid and effective
Interleukin
Type of cytokine
Communication between leukocytes
Interferon
Type of cytokine
Fights viruses
Chemokine
Type of cytokine For chemotaxis (ie neutrophil extravasion)
Passive vs active immunity
Passive is via transfer of antibodies or cells (ie breastmilk)
Active is response from patient’s cells
Types of immune receptors
Innate:
- PRR - pattern recognition - non-specific for bacteria, virus
- self - NK and cytokines
- FcR - bind to antibodies and direct innate cell function (NK, PMN, macrophage, eosinophil, mast)
Specific:
- Ig on B cells (specific for antigen)
- TCR (specific for MHC + peptide)
General receptor function
External light chain yields specificity
Internal structure + function are constant
Most fx through aggregation and crosslinking
Can either be constant expression or induced
Innate immune system
Nonspecific -> rapid (hours), same with reinfection
Detection and activation of specific responses
Includes:
- acute phase proteins
- complement
- macrophages
- neutrophils/PMNs
- NK cells
Phases of immune response
Antigen recognition -> presentation ->
Lymphocyte activation (clonal expansion, differentiation)
Effector phase (humoral and cellular)
Contraction via homeostasis -> memory cells
Antigen presentation
Presentation of proteins + MHC for recognition by TCR Professional APCs: - macrophage/mononuclear system - ex dendritic cells - some B cells
MHC
Major histocompatibility complex
MHC I - all nucleated cells, presents sample of internal proteins -> CD8 cell (recognizes if this cell is infected)
MHC II - only APCs, presents external proteins -> CD4 (recognizes presence of external invader)
Adaptive immunity
Specificity of response via receptors
- Ig on B cells
- TCR
Memory from memory cells
Immune activation signals
Two separate signals needed!
Signal 1 = antigen (B cell Ig) or MHC + peptide (TCR)
Signal 2 = costimulatory from cell in distress
(ex can get autoimmunity from too many costimulatory signals)
Clonal expansion
Activated lymphocyte rapidly divides -> clones with same specificity of receptors
Most become effectors
10% become memory
General antibody properties
Antibody = immunoglobulin = Ig
5 types: IgM, IgD, IgG, IgE, IgA
Fab - antigen binding domain - usu multiple sites for same antigen
Fc - effector portion -> differentiation (migrate, gain of fx), cytokines (recruitment), release of granules (PMN, eosinophil, mast, NK, cytotoxic), etc
Types of T cells
Cytotoxic = CTL = CD8
Helper = Th - direct immune response
- ex CD4, Th1 (inflammatory), Th2 (antibodies), Th17 (autoimmune)
Regulatory = Treg - suppress immune response
Lymphoid tissues
Drainage and organs designed for maximum interaction between APCs (dendritic) and circulating T-cells
Primary - marrow and thymus -> dev’t
Secondary - nodes, spleen -> interaction
