5. Adaptive Immunity - Lymphoid Organs, Lymphocytes and Receptors Flashcards
What are the three major groups of receptors that help sort out what should/shouldn’t be in the body?
PRRs to recog molevules common to pathogens
Major Histocompatibility receptors (MHC) - recog normal cell surface MHC proteins
Lymphocyte antigen receptors - recog antigens (proteins/sugar chains) NOT normally present
How was MHC discovered?
by tissue grafts with mice. They could transfer tumor tissue successfully btw closely related mice - not b/tw mice of dif strains - unless you first killed their immune system. So tissues carry antigens unique to that individual
How many regions are the MHC genone divided into?
MHC 1, 2 and 3Desc
Describe and explain how MHC type 1 works
Marks cell as self
found on cell surface of most nucleated cells within host tissues, genetically same in given individual, used by NK lymphocytes to ID cells as normal. binds to internal ports. + displays them on cell surface (have binding site for lymphocytes so can check out int. prots. + helps T lymphocytes recog viruses, tumors, foreign grafts) most nucleated cell types in body display MHC antigens except RBC (+/- neurons, sperm, ova, cells forming on placenta). blood transfusions btw anims is easy, tissue grafts impossible
Describe how MHC 2 works
found on professional phagocytes + antigen presenting cells
fragments of pathogen or damaged tissue are broken down into antigen and attached to antigen presenting receptors (antigen presenting receptors are type 2 MHC molecules) antigen presentation is req to generate an adaptive immune response
What functions does MHC 3 have?
PRRs, signaling molecules, complement components
What are Lymphocyte antigen receptors?
found on T + B cells but not NK cells
receptors on B are released -> antibodies. T-cells have antibody like receptors.
genetic material randomly re-arranged + modified - allows for diversity and inc chance of Ag binding
on each lymphocyte the lymphocyte antigen receptor binds to only 1 specific antigen
only cells w/ receptors for non-life allowed to survive - if cells attack host, destroyed by apoptosis
How do T- lymphocytes work?
prod in bone marrow, mature in thymus, reside in lymph nodes + spleen and circulate in blood and tissue
predominant lymphocyte found in blood
carry 2 types of receptors (lympho antigen recept. + receptors for MHC antigens (self) are next to each other)
T cells bind to other cells using MHC and test the displayed antigens using lympho antigen recept
How are t-cells ‘educated’?
occurs in thymus. initially t cells selected for cells that will recog MHC receptors (self) so that they can communicate with other cells
further selected for lymphocyte antigen receptors that are not activated by self antigensW
What is the function of T-Lymphocytes?
adaptive immune response
effector cell line for cell mediated immunity - specific( the receptors on the cells are randomly generated so one cell recogs ONE antigen)
What is tolerance?
failure of the immune system to respond to an antigen at a second or subsequent presentation
an important method of telling self from non-self. Normal t Lymp are tolerant of normal tissue
respond the first time, but not the second
What is the relationship between tolerance and dz?
tolerance can also happen to pathogens if they are present in the fetus
cows with BVD infection 45-120d of gestation (t cells react with BVD are removed, persistent infection)
How does T-cell activation works?
t-cell lymp ant recept binds its specific antigen, req ag presentation. Typically abnormal protein displayed on MHC molecule (virus infected cell w/ virus antigen on surface, dendritic macro display on surface bits of material it has phagocytosed)
Dendritic cells use PRRs to ID pathogens/damged cells, phagocytose, degread eaten material, components displayed on surface with MHC antigen -ag presentation, dendritic move to lymp nodes, multiply and differentiate and get activated by an antigen
What is the role of dendritic cells in T-cell activation?
reside in tissues. use PRRs to ID pathogens and damaged cells, phagocytose them and degrade ingested material then take components of material and display them of surface w/ MHC antigen - Ag presentation, then move to lymph nodes where it activates the specific t-cell (with a receptor for that antigen, initial activation called priming) then multiply + differentiate (new cells clones of original cell and recog same antigen), when activated by antigen- concentrated at sites of inflam and draining lymph nodes
What do t lympocytes differentiate into?
Helper T Cells - stims immune response, short-lived
Suppressor T cells - tone down immu response
Cytotoxic T cells - kill infected/abnormal cells - recog non-self antigens (bound to MHC complex) and destroys cells by releasing interferon (shuts down virus prod) and perforin to punch holes in cell)
memory T cells - more rapid response when same antigen presented
What are memory T cells?
Some move to ares of inflam, others to lymph nodes, rapid response when SAME antigen is seen again - more cells, better cells
long lived - this is why vx work
What is T-cell mediated immunity?
takes time to develop (d to Mo)
specific for particular antigen
involves memory so more rapid + efficient at a second presentation
Ex. of adaptive immunity
important for viral infections, graft rejection and essential for B cels to work (part of second signal)
How can the body Id self from non-self?
self does not have surface molevules that react w PRRs
self has appropriate MHC rantigens (some lympho check specifically for this- NK killer lymphoc)
lympho are tolerant to self-antigens normally displayed on cell surface - no lymp antigen recept for self molecules
