Bridging Innate and Adaptive Immune Flashcards
Cytokines
Effects
Regulation of growth
Differentiation
Gene expression of different cell types
Phagocytosis: Basics
What it does and process
- Phagocyte engulfs particle
- Helped by opsonins which label the target to engulf
- Cytoplasm flows around particle, fuses with it = pseudopodia
- Pseudopodia increase in oxygen, oxidative burst
- Phagosome moves to center of cell
Phagocytosis: Fusion and Digestion
Process
- Cytoplasmic granules fuse with phagosome = turn into phagolysosome
Degradation - Granule proteolytic enzymes: oxygen independent
- Toxic peroxidase: oxygen dependent
Antigen Presenting Cell (APC)
What are they? Who are they?
Cell that can take up, break down, display parts of pathogen to other cells
Macrophages, dendritic cells, B cells
Present antigens to T cells
Antigen Definition
Substance that can be specifically bound by an antibody or T cell receptor
Peptide Definition
Antigen that is bound by a T cell receptor
Antigen Bound by Antibody, Immunoglobin, or B cell Receptor
Sugars, phospholipids, nucleic acids, proteins
Immunogen Definition
Molecules that stimulate immune response, important for deciding what antigen we pick for a vaccine
Epitopes
What are they and different recognition by cells
Specific determinant on the antigen that can be recognized by the immune system
- Immunogens can have mulitple epitopes
B cell: recognizes both linear and discontinuous/conformational epitopes
T cell: recognizes linear epitopes as part of MHC proteins, immunogen must be degraded
Major Histocompatibility Complex Basics
Genetic region in living things responsible for presenting antigen lymphocytes
- Expressed in antigen presenting cells or all nucleated cells
“Human leukocyte antigen (HLA)” molecules present both self and foreign antigens
MHC Gene Categories
Three classes
MHC Class I: antigen recognition; HLA-A, B, C of chromosome
MHC Class II: antigen recognition; HLA-D of chromosome DP, DQ, DR
MHC Class III: secreted proteins in area between class I and II genes
MHC Genes
Codominantly expressed
Travel together during inheritance - haplotype (genes for A, B, C, DR, DP, and DQ) from each parent
MHC Class I
Binds peptides within cells
- of internal origin (virus/tumor)
- Transport/present to plasma membrane for CD8 T/cytotoxic T cells
- Found on all nucleated cells
MHC Class II
Bind peptides within cells
- external origin (bacteria)
- transport and present to plasma membrane for CD4 T cells/helper T cells
- Only found on antigen presenting cells
What Causes Increase in MHC Expression?
Inflammation and adaptive responses
MHC Structure
4 main things
- Extracellular binding groove, immunoglobin domains, transmembrane segments
- Polymorphic sites mostly in or near binding cleft
- Non-polymorphic sites in Ig domains bind CD4 and CD8 on T cells, docking mech.
- Filled with “self” peptides when no infection, marks that cells are healthy and normal
Role of MHC
Main: antigen presenting
- pick up degraded peptides in cells, transport to plasma membrane and present to T cells that recognize it
Differences: related to mechanism of how antigen is transported to surface
Class I MHC-Peptide Interaction
Synthesized in endoplasmic reticulum
Endogenous pathway: antigens synthesized in same cell as Class I molecules
- self antigens, intracellular peptides
- peptides that bind to Class I molecules 8-11 amino acids, from partial digestion of proteins
CD8 T cells always check cell surface for non-self antigens, produces cytokines if they are present
Class II MHC-Peptide Interaction
Synthesized in endoplasmic reticulum
Exogenous pathway: antigen taken into the cell from outside by phagocytosis or endocytosis
- Invariant chain: prevent binding of endogenous peptides within endoplasmic reticulum
- Must be transported from ER to endosomal compartment to bind with peptide
Significance of MHC
- Determinant of transplant compatibility
- Certtain alleles protective for infectious diseases
- Certain HLA antigens increase autoimmune disease risk
- Role in cancer prevention or development
