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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

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