39 terms

Bio Exam #3 - Akkaraju - Immune System

Innate immunity
- nonspecific
- present before exposure to pathogens, always present
- first line of defense, quick
- effective from time of birth
- external barriers + internal cellular and chemical defenses
- activates adaptive immune system
Adaptive immunity
- very specific, very strong
- second line of defense, takes time to respond
- absorbs pathogen, recognizes it & develops a specific response
Physical barrier
- skin
- mucus secretions - bacteria and fungi get stuck and become immobilized - traps agents
- cilia push pathogens down and out
- low pH
Antimicrobial peptides
Innate - Found in secretions - small proteins that attack microbes directly or impede their reproduction
Innate - Activate microphages - nonspecific - responsible for illness symptoms (aches, tiredness)
Innate - Macrophages & neutrophils - engulf pathogens and destroy them in the liposomal compartment - use pathogens to warn immune system
Toll-like receptors (TLRs)
Innate - Proteins found on cells - recognize certain ligands (ex: lipopolysaccharides found on surface of bacteria) - initiate a signal transduction cascade that activates inflammatory response
Innate - Contain granules that are enzymes that can attack and destroy pathogens
Dendritic cells
Innate - Swallow pathogen, break it up into pieces & stick pieces out onto surface of cell to activate adaptive immune response - present pieces of invading pathogens to lymph nodes
Mast cells
Innate - Release histamine
Innate - Diffuse through extracellular matrix and get inside blood vessels - spread word of invasion - cause cells to move to site of infection
Blood vessels become leaky - increased vascular permeability so cells can get out and move towards site of infection - fluid also leaks out, cases swelling (symptom)
Innate - Local or systemic (throughout the body) - fever is a systemic response triggered by pyrogens released by macrophages
Septic shock
Body overproducing cytokines all over body - anaphylactic shock - usually over reacts the second time - happens when all blood vessels become leaky and blood pressure drops
Natural Killer (NK) Cells
Innate - look for cells that don't have anything sticking out on surface (abnormal) - assume that the cell is infected & will kill the cell
Adaptive - white blood cells that carry pathogen-specific receptors on their surface - T cells & B cells which both recognize specific structures on antigen
T cells
Adaptive - mature in thymus - hundreds of thousand different T cells looking for the one antigen they were born to recognize
B cells
Adaptive - humoral immunity - mature in bone marrow - hundreds of thousands of B cells that recognize different antigens on different pathogens or viruses- produces antibodies that recognize epitope on antigen
anything that can be recognized by B cell or T cell - specific regions called epitope are the areas that receptors on B & T cells recognize
MHCs (Major Histocompatability Complex)
group of proteins that are found on the surface of all our cells - identify cells as self, not foreign
present on ALL cells of body - interacts with T cell receptor on CD8+ T-cells (HIV infects CD8+ T-cells)
present on antigen presentation cells only - interacts with T-cell receptor on CD4+ T-cells
coreceptors to T cell receptors - binds the class II MHC - T cells need CD4 (like 2 hands feeling the MHC molecule & peptide)
Helper T cells
when activated, secrete cytokines that stimulate other lymphocytes - activate cytotoxic T cells
Cytotoxic T cell
cell mediated killing - make CD8 which interacts with class I MHC - when it binds to MHC I on infected cell, it activates a cytotoxic T cell and makes it an active killer, which secretes proteins that destroy infected target cell
makes pores/holes in membrane target cell
Enzyme that enters the cell through pores and triggers apoptosis
Clonal Selection
generates antibody-secreting plasma cells, the effector cells of humoral immunity
Lymphocyte Diversity
1. one gene for every BCR & TCR
2. a few genes that can mutate constantly
- differences in variable region account for specificity of antigen receptors
- Ig (immunoglobin) gene encodes one chain of the B cell receptor
- many different chains can be produced from the same Ig chain gene by rearrangement of DNA
- rearranged DNA is transcribed and translated and the antigen receptor is formed
--- recombination between V, J and C
Long term immunity
memory B and T cells
Bacteria that have entered the body
killed by being bound to complements
primary immune response
first exposure to a specific antigen - effector B cells called plasma cells are generated, and T cells are activated to their effector forms
secondary immune response
memory cells facilitate a faster, more efficient response
coating the virus with antibodies to physically block the cell surface of the virus
antibodies bound to antigens increase phagocytosis
membrane attack complex
proteins of the complement system join antibodies --> create pores on the surface of the bacteria --> ions flow in --> cell expands --> cell lysis
nonpathogenic form of a microbe or part of a microbe is injected in order to elicit an immune response to generate an immunological memory cell population (active immunity)
Passive Immunity
acquire immunity by acquiring antibodies against it - can be injected into sick patient or IgG crosses the placenta or IgA passes through breast milk
Graft rejection
MHC cells are different among genetically non-identical individuals --> stimulate rejection of tissue grafts and organ transplants