Immunology Unit 1

Immune System Stages

Immunological barriers, innate immune system, adaptive immune system, immunological memory

Three types of barriers

Mechanical, chemical, microbiological

Examples of mechanical barriers

Skin, flow of tears/saliva, cilica

Weaknesses in mechanical barriers

Abrasions in skin, evaporation of mucous/tears/saliva

Examples of chemical barriers

antimicrobial peptides in sebum, tears, and saliva, low gut pH of stomach acid

Weaknesses in chemical barriers

Loss of substances containing peptides caused by environment or medications, dilution of stomach acid

Examples of microbiological barriers

mutualistic microbiomes/normal flora

Weaknesses in microbiological barriers

Good bacteria inhabit a niche, if something wipes them out like an antibiotic then bad bacteria inhabit it instead

Innate Immune System

In all tissues, best at killing bacteria, include complement, macrophages, neutrophils, NK cells, and granulocytes

Complement

Soluble proteins that work to cause inflammation, opsonization, and membrane attack complexes as part of the innate immune system

Opsonization

Makes the pathogens tastier so the phagocytes eat them faster

Membrane attack complex

Attack the cell walls of bacteria to goosh them

Innate immune system cells

Macrophages, neutrophils, NK cells, granulocytes (mast cells, eosinophils, basophils)

Inflammation

Recruits immune cells, caused by cytokines that are secreted by immune cells, act on vascular endothelial cells, modify tight junctions to allow vascular permeability (vasodialation). Fluid leaks out causes swelling etc, allows white blood cells to migrate out of the blood vessel to the infected tissue.

Macrophages

Live in your tissues, first responder, recognize pathogens, release inflammatory cytokines, recruit immune cells, phagocytose pathogens, repair damage

Neutrophils

Circulate bloodstream, recruited by inflammation, phagocytose 6-8 bacteria and explode, release sticky chromatin that traps bacteria in a Neutrophil Extracellular Trap

Natural Killer Cells

Throughout body, kills infected, tumor, or stressed cells, have inhibitory and activating receptors. Healthy cells express inhibitory ligands, unhealthy cells express activating ligands (MIC) which tells the NK to kill it with apoptosis causing cytotoxins. They don’t have specific targets, they just patrol.

Adaptive Immune System

In lymphoid tissues, contains primary and secondary tissues

Primary lymphoid tissues

Thymus and bone marrow, develop lymphocytes

Secondary lymphoid tissue

Spleen, lymph nodes, tonsils, deploy lymphocytes

T-cells

Developed in thymus, helper CD4 T-cells activate macrophages and B cells, cytotoxic CD8 T-cells kill virus infected cells

B-cells

Once active, differentiate into plasma cells, secrete antibodies that opsonize, activate complement, and neutralize

Immunological memory

Memory cells and long lived antibodies, outnumber pathogen-specific naive lymphocytes, activates quicker, respond to infections sooner, inhibits activation of naive lymphocytes

Antigen

Anything that can be recognized by a BCR or TCR

Antigen specificity

Each BCR/TCR only has receptors for one type of antigen, genetic recombination randomly causes trillions of receptor types, at a certain age your thymus atrophies so no more T-cells