Intro to Immunology Flashcards
____ is the reactive portion of an antigen
epitope: chemically reacts with antibody to form antigen-antibody complex aka immune complex
fun fact: antigen = anti[body] gen[erator]
cells of hematopoietic origins can be phenotypically characterized by the pattern of ____ markers expressed at any given time
CD markers (cluster of differentiation) - cell membrane molecules, defined by the reference monoclonal antibody to which they bind
many CD molecules, cells express more than one CD marker:
- helper T (CD4): CD3+, CD4+
- killer T (CD8): CD3+, CD8+
- Tregs: CD3+, CD4+, CD25+
what CD markers are expressed on helper T, killer T, and T regulatory cells?
helper T: CD3+, CD4+
killer T: CD3+, CD8+
Treg: CD3+, CD4+, CD25+
how is immune tolerance achieved
under conditions that suppress immune system - NOT simple absence of immune response
3 functions of macrophages and DC cells
- phagocytosis
- secrete cytokines
- antigen presenting (APC cells)
*develop in bone marrow but acquire specific functions later within tissues
match:
B, T lymphocytes, natural killers
with
innate, humoral, cell-mediate immunity
natural killers: innate immunity (also considered lymphocytes)
B lymphocytes: mediate humoral immunity
T lymphocytes: mediate cell-mediated immunity
what are the antigen-presenting cells, and in what immune response do they participate?
- DC (dendritic cells) - initiate T cell response (*only cells that can initate T cell response alone)
- macrophages - present to T cells, which activate macrophages to kill microbe (cell-mediated immunity effector)
- follicular dendritic cells - display to B lymphocytes in humoral immune response
- B cells - display to T lymphocytes, which activate B cell antibody production (humoral immunity)
what are the effector cells (elimination of antigens) of the immune system? (3)
- T lymphocytes (CD4/CD8)
- macrophages (derived from monocytes)
- granulocytes (neutrophils, eosinophils)
what immune cells develop from:
1. myeloid progenitor
2. lymphoid progenitor
- myeloid: megakaryocytes, erythrocytes, granulocytes, monocytes (-> macrophage)
- lymphoid: T cells, B cells, NK (natural killer) cells
*note that DC (dendritic cells) are from both
These immune cells respond to interleukin-12 (IL-12) produced by macrophages, and secrete interferon-y (IFN-y) to activate macrophages. They work at the boundary of the innate and adaptive immune systems. What is?
natural killer (NK) cells
how is antigen receptor diversity generated to be able to deal with endless amount of mutating/evolving pathogens?
V-(D)-J Recombination of TCR/BCR genes - requires recombination activating genes (RAG1 and RAG2)
V and J segments are cut and pasted (fused) together in random/messy fashion
(D/diversity segment is not always present, but goes through recombination when it is there)
function of RAG1 and RAG2
recombination activating genes - essential for TCR/BCR diversity via V-(D)-J Recombination
structure of TCR compared to antibody (be specific)
TCR (in membrane): heterodimer - alpha and beta chain, variable and constant region of each chain (constant region closest to cell membrane)
antibody (secreted): Fab heterodimer contains antigen-binding site - light and heavy chain with variable and constant region of each, Fc region (constant fragment) interacts with Fc receptors on innate immune cells or with complement system
role of Fab and Fc region of antibodies?
Fab contains antigen-binding site (light and heavy chains with variable and constant region)
Fc (constant fragment) interacts with innate immune cells and complement system
what happens in Type 1 diabetes?
random generation of antigen receptors can lead to autoimmunity
Type 1 diabetes: T cells attack/kill insulin producing beta cells within Islets of Langerhans
central tolerance vs peripheral tolerance (in the immune system)
central tolerance: removal of self-reactive clones - occurs in thymus (T cells) and bone marrow (B cells)
peripheral tolerance:
1. ignorance - hide self-antigens
2. anergy - shut down self-reactive clones
3. suppression - suppress self-reactive clones
contraction phase of immunological memory
immune cells initially produce a lot of themselves, during contraction phase they reduce their number (to prevent too strong of an immune response)
2 primary sites of immune system activation
- lymph nodes
- spleen
match:
1. exogenous antigen, endogenous antigen
with
2. MHC I, MHC II
with
3. CD4, CD8 T cells
with
4. virus, bacteria
with
5. all cells, APC only
exogenous antigen (bacteria) —> MHC II —> CD4 T cells
only present on APC
endogenous antigen (virus) —> MHC I —> CD8 T cells
present on all nucleated cells
[remember that MHC is a self-protein that binds an antigen peptide - MHC-peptide complex marks the cell as infected and activate T cells]
all nucleated cells express MHC[I/II], but only APC cells express MHC[I/II]?
what are the profesional APC?
all nucleated cells: MHC I (endogenous antigens - viruses) —> CD8 T cells activated
APC (DC, macrophages, B cells): MHC II (exogenous antigens - bacteria) —> CD4 T cells activated
antigens must be mixed with ____ to activate the immune system
adjuvant: agent that stimulates immune system but does not have a specific antigen effect itself
—> innate immune response precedes adaptive response
pattern recognition receptors are a part of ____ immunity
pattern recognition receptors of INNATE immunity recognize pathogen-associated molecular patterns (structures shared by a class of microbes)
example: Toll-like receptors, mannose receptor, scavenger receptor
function of Toll-like receptors (TLR1-TLR9)
receptors of innate immune system
recognize dsRNA, LPS, flagellin, CpG DNA, viral ssRNA, etc
in the SARS-CoV-2 virus that causes COVID19, the viral _____ binds ____ on host cell membrane
viral RBD (receptor binding domain) binds ACE2 on host cell membrane
viral RBD is on top of viral spike protein
neutralizing antibodies that block RBD from binding ACE2 are therefore very effective
