10 - Cell-Cell Communication: Immunology

Mechanical barriers

leaf cuticle, insect exoskeleton, snail shell, human skin, coughing/sneezing, flushing (tears)

Chemical barriers

Antimicrobial peptides, digestive enzymes (lysozymes) in saliva, tears, and breastmilk

Biological barriers

Healthy microbe populations

MHC Class I

the 1 thing found on all cells ... but RBCs

MHC Class II

Found on antigen presenting cells

Clonal Selection Theory

Lymphocytes carry unique receptors; only when there is a match with an antigen are they activated; they then undergo clonal expansion; Lymphocytes with receptors that do not bind eventually die

Cytotoxic T cells

Kills cells that are infected with an intracellular pathogen

Helper T cells

Releases cytokines to activate cytotoxic T cells (Th1) and B cells (Th2)

How are extracellular pathogens eliminated?

Eliminated through a combination of antibody production of plasma cells (humoral response) and activated phagocytosis

Opsonization

Enhances phagocytosis; Antibodies coat the surface of a pathogen, which “tags” the pathogens, making it easier for phagocytes to recognize and eat it

Neutralization

Antibodies coat the surface of a pathogen, which blocks the pathogen from entering of attacking your cell

Agglutination

Antibodies have two arms, so they can bind to two pathogens at once. This causes pathogens to stick together into big clumps, making it easier for phagocytes to spot and destroy

Co-stimulation of complement proteins

Antibodies bound to a pathogen can activate the complement system. Complement proteins can form a Membrane Attack Complex (MAC) that punches holes through the pathogen and kills it.

Second Exposure: Memory

Secondary response is faster and more efficient because memory T and B cells are there with the correct receptors

Epitopes

The specific part of an antigen that is recognized by the immune system

How are variable regions created?

GENETIC recombination in immature B and T cells

How was genetic recombination in B and T cells discovered?

Scientists noticed that the genes were longer in immature B and T cells, which meant they still had all the original DNA segments