Lecture 11 - Immune System Flashcards

Question

Types of MHC cells

Answer 1

Class I MHC Complex - present on surface of all cells in the body - when cellular proteins are degraded, fragments are carried to plasma membrane and presented on MCI outside of cell - sampling of all components in the cell, normal or not - detects infections of mutations - recruits cytotoxic (killer) T cells Class II MHC compelx - found on surface of APCs - when the APC ingests a pathogen through phagocytosis, the pahtogen is broken down and a fragment is carried to the cell surface - recruits helper T cells

Answer 2

- B cells make antibodies (can secrete them or express them on cell surface, bind to specific antigen) - first time antigen is encountered, it is detected by binding to the antibody receptors on the B-cell surface (with help from Th cells) - activates B-cell to make and secrete multiple copies of the antibody

Answer 3

- all have a common structure - tetramer of 4 polypeptide chains - two are identical light chains - 2 are identical heavy chains Each chain has 2 regions 1. constant regions - shared amino acid sequences - determine whether it will be an integral membrane receptor or a soluble antibody secreted into the blood stream 2. variable regions - different for each type of antibody - specificity of antigen binding - two identical antigen binding sites on each antibody

Answer 4

- one B-ell makes a specific type of antibody - enormous diversity of different B-cells exist, each of which makes a different type of antibody - one antibody reacts with a specific antigen Proliferation - when an antigen binds to a B-cell, it (with Th cells) stimulates it to proliferate to form a group of identical C cells - all of these clones produce and secrete antibpdies with that same sepcificity as the activated B-cell

Answer 5

Activation: sepcific Th cells are activated and proliferate - APC presents antigen via Class II MHC complex - T helper cell binds to APC - specific receptor that binds specific antigen - Th cell releases cytokines - cytokines activate Th cell to proliferate, producing clones of Th cells with the same specificity

Answer 6

Effector phase: activated Th cells activate specific B cell to proliferate and produce antibodies for secretion B Cells act as APCs - B cells have antibodies bound to cell surface that serve as receptors to which antigens can bind - pathogen binding to this antibody is internalized and broken down and antigen is displayed by MHCII complex of B cell - activated Th cell binds to a Bcell that is presenting the correct antigen (same antigen as it originally encountered in the initial APC) - cytokines released by Th cells activate B cells - activated B-cell proliferates and synthesizes antibodies

Answer 7

Th cell stimulates B Cell to divide, differentiate and produce antibodies Gives rise to two types of B cells: 1. effector B cells (plasma cells) - secrete antibodies into bloodstream - all effector cells arising from a given B cell produces antibodies that are specific for the antigen that originally bound to the parent B cell 2. Memory cells - long lived stand by's that are ready to amp-up the immune system quickly if re-exposed to a pathogen - allow for lasting immunity against pathogen

Answer 8

OPSONIZATION - antibody stimulates removal of pathogen by macrophages - tag a microbe or an infected cell for phagocytosis NEUTRALIZE TARGET - block pathogen's ability to enter cells AGGLUTINATION - link pathogens together into large complexes - become easy targets for phagocytes TRIGGERING OTHER IMMUNES PATHWAYS SUCH AS COMPLEMENT SYSTEM - marks pathogen for phagocytes - helps kill the pathogen directly

Answer 9

- cell that has been infected by a virus or undergone mutations will contain foreign or abnormal peptides - will present these on cell surface as Class I MHC complex - Cytotoxic T cells recognize and bind to this comples - Tc cell activation and growth is promoted by activated T cells - activation of a specific T cell triggers selective proliferation of that type of T cells - these activated Tc cells now bind to any cell tha tis displaying an antigen on its Class I MHC receptor (and therefore is infected)

Answer 10

CELL LYSIS - activated Tc cells produce a substance called perforin - peprforin lyses the cells that the Tc cell has bound to via MHC I complex PROGRAMMED CELL DEATH - Tc cells can also bind to a different receptor on the target cell that initiates apoptosis in that cell - work together to eliminate antigen containing host cell - help rid body of its own virus-infected cells

Answer 11

- activated lymphocytes (B or T cells) divide and differentiate to produce two types of daughter cells EFFECTOR CELLS - carry out attack on antigen - effector B cells secrete antibodies - effector t cells secrete cytokines and other molecules that destroy pathogen cell - only live a few days MEMORY CELLS - long lived cells - retain ability to start dividing on short notice to produce more effector and memory cells - many survive in body for decades

Answer 12

1. Primary - when body first recognizes an antigen, naive lymphocytes that recognize the antigen proliferate - lag time - takes a while for number of B and T cells to slowly increase 2. Secondary - subsequent encounters with the same antigen - memory cells bind antigen and rapidly proliferate - launch army of B and T cells - much more rapid and powerful response

Answer 13

- can come from previous exposure to pathogen | - can come from vaccines

Answer 14

introduction of the antigen into the body in a form that doesnt cause disease Ways: INACTIVATION - kill pathogen with heat or chemicals ATTENUATION - live but not toxic - cultured in the lab to get mutations that make it harmless PEPTIDE SUBUNIT - recombinant DNA technology - do not introduce a whole microorganism to the immune system, just a part of the antigen protein - peptide fragments that can bind and activate lymphocytes but do not have the harmful part of a protein Then: - initiate primary immune response, generating memory ells without making the person ill - memory cells already exist if person encounters pathogen later

Answer 15

- overreact (allergic reaction) - attack self antigens (autoimmune) - function weakly (immune defficiency)

Answer 16

- immune system overreacts to a dose of antigen - exposure to an antigen causes B-cells to make a large amount of a specific type of antibody that takes up residence in cell membrane of mast cells - if individual is re-exposed to that allergen, the allergen binds to these antibodies on the mast cells - causes the mast cells to secrete a large amount of histamine - dilation of blood vessels, inflammation

Answer 17

T cells or antibodies that bind self-antigens - during development of lymphocytes, cells that make antibodies against self antigens that should have been destroyed were not - molecular mimicry - T cells that are designed to recognize a non-self antigen may accidentally recognize something in he self antigen that has a similar structure

Answer 18

- highly vulnerabel to infections and cancer - B or t cells never form - B cells lose ability to give rise to effector cells - HIV (aids) - infects and destorys helper T cells - killed by both the virus itself and Tc cells the destroy infeted cells

Answer 19

Lupus - b cells produce antibodies against the body's own nuclear proteins rheumatoid arthritis - inability to shut down a t cell response - inflammation in the joints hashimoto's thyroiditis - immune cells attack thyroid tissue, resulting in fatigue, depression, weight gain type i diabetes - immune reaction against cells in pancreas that produce insulin MS - immune system attacks and damages myelin myasthenia gravis - antibodies block acetylcholine receptors on muscle cells - muscle weakness