Test 4/Final Flashcards
pathogen
anything that causes disease. (microbes like bacteria or pollen, secretions like venom, non-self tissue, some cancer cells)
antigens
cell surface proteins that body recognize as non-self. pathogens have antigens.
WBC
protect the body against pathogens. some circulate through lymph, blood, and interstitial fluid and some are housed in lymph nodes, thymus gland, spleen, appendix, etc.
Innate immunity
born with this immunity, broad– any pathogen is targeted.
Innate immunity: first line of defense
Includes skin as a barrier, mucous membranes to trap, and secretions in mucous membranes with anti-microbial proteins. Stomach secretes acids.
Innate immunity: second line of defense
non-specific WBC attack. Ingest and destroy microbes. Neutrophils, monocytes (macrophages), dendritic cells, eosinophils, basophils
neutrophils
most abundant WBC, short lived
macrophages
develop from monocytes. large and long-lived
dendritic cells
stimulate acquired immune system
eosinophil
destroy multicellular parasites by releasing toxic enzymes.
basophils
contribute to inflammatory and allergic responses.
lysozymes
lysozymes work in macrophages and in saliva, tears, and mucous.
Interferons
limit intra-cellular spread of viruses.
complement proteins
result in lysis; also help trigger inflammation and activate acquired immunity
defensins
secreted by macrophages, attack pathogens
natural killer cells
attack virus-infected cells and cancer cells
inflammatory response
usually localized in response to injury. Causes swelling as fluid and immune cells leak out of blood
Invertebrate Innate defense system
amoeboid cells in echinoderms, insect exoskeleton, hemocytes in insect hemolymph function as WBC, they have little immune system memory
acquired immunity
develops over time in response to exposure to pathogens. Highly specific. Includes b and t cells.
How does blood access immune system structures?
Since the lymph system is closely tied to the circulatory, pathogens in blood and exposed to phagocytes and lymphocytes in the lymph system
antigen recognition
recognized by antigens. most pathogens have several antigens, so several different lymphocytes recognize and respond to it
epitopes
specific binding sites on all antigens
lymphocytes (b and t cells)
each lymphocyte only recognizes a single antigen, but the receptor molecules and recognition process are different b/w b and t cells.
constant vs. variable regions
constant regions have stable amino acid sequences from cell to cell while variable regions have different amino acid sequences
b-cell receptors and antigen recognition
are y-shaped and each branch has two parts called chains. Inner, heavy chain makes full Y while outer light chain is located on the branches of the Y. both chains are proteins linked by chem. bonds. Both chains have variable amino acid sequences that act as antigen binding sites and bind to epitopes.
t cell receptors
unbranched with alpha and beta chain chemically linked with a single antigen binding site at the terminus.
T cell antigen recognition
recognize antigen fragments that have been bound to a self-cell protein called MHC. Does not recognized intact antigens on intact pathogens.
MHC
major histocompatibility complex; bind to antigen fragments at surface of cell and T cells detect presented antigen+MHC complex. Very varied among individuals due to multiple alleles. Very rare for people to have the exact same MHC
Class 1 MHC
found in most nucleated cells and bind to antigen fragments if cell has been infected or is cancerous. Class 1 MHC antigen complexes are recognized by cytotoxic T cells and they then destroy the “sick” cell
Class II MHC
found in dendritic cells, macrophages, and B cells. Presents antigens from pathogens that have been engulfed by phagocytosis. Recognized by helper T’s and begin a cascade of event to control the infection
difference between b and t cell receptors
b cell receptors bind directly to antigen on intact pathogen and t cell receptors bind to MHC+antigen complex on self-cells.
lymphocyte overview
produced from stem cells in bone marrow, some mature in the bone marrow (b cells) and rest mature in thymus (t cells)
maturation of lymphocytes overview
the development of b and t cell receptors. Once mature they either stay in organs of lymph system or circulate throughout blood, lymph, and interstitial fluid
lymphocyte development steps
- generation of diversity
- testing and removal
- clonal selection
lymphocyte development step 1
generation of diversity: genes that code for the antigen receptors are randomly rearranged by enzymes. during differentiation of each B cell one variable segment is snipped out and attached to one joining segment.
If the coding gene has 40 variable segments and 5 joining segments, how many total combinations are possible?
200
V+J segment is attached via an ________ to the ___ segment that codes for the constant region of the light chain
intron, constant
what is the difference between heavy and light chain DNA coding
while the light segment has 40 Variable segments and 5 Joining segments, the heavy chain has more V segments
lymphocyte development step 2
Testing and removal: each new receptor is tested against self cells during development and migration into lymph system organs. Receptors that bind to self cells or self MHC molecules are eliminated or deactivated.
lymphocyte development step 3
clonal selection: each b and t cell has receptors that are specific to a single antigen. Incoming pathogens typically display several antigens, and when a lymphocyte receptor encounters a matching antigen the lymphocyte is activated. 2 clonal populations are formed: effector cells and memory cells
