Immune System

what are they two categories of innate (non-specific) defence?

surface barriers + internal defences

what are included in both of the categories of innate defence?

surface barriers:

• skin

• mucous membranes

Internal defences:

• phagocytes

• natural killer cells

• antimicrobial proteins

• inflammation

• fever

what are phagocytes + the two specific cells that are phagocytes?

• phagocytes destroy foreign particles via phagocytosis, then lysosomes destroy it

• neutrophils and macrophages

what are natural killer cells + their mode of killing?

• second most common defensive type

• kills cancer and viral infected cells

• kill it by directly contacting target, and injecting enzymes to make the cell undergo apoptosis

purpose of inflammation?

• is tissue response to injury

• Prevents spread of damaging agents to nearby tissues, disposes of cell debris and pathogens, alerts adaptive immune system and set the stage for repair.

• Releases histamines

purpose and effects of fever?

• Widespread response to invasion. Is abnormally high body temp, and is systemic response to invading microorganisms.

• Causes liver and spleen to sequester iron and zinc → makes them less available to support bacterial growth.

• Increases metabolic rate of tissue cells.

what are antimicrobial proteins + what they do

• Interferons – signalling proteins that interfere with virus replication by synthesising proteins to block further protein synthesis and degrade viral RNA

• Complement [system] – group of 20+ plasma proteins that circulate in blood in inactive state. Complements (enhances) effectiveness of both innate and adaptive defences

what are the three complement pathways?

• Classical – activated by antibodies coating target cell

• Lectin – activated by lectins binding to specific sugars on microorganisms surface. They recognise foreign invaders

• Alternative – activated spontaneously. Lack of inhibits on microorganism’s surface allows process to proceed

what are the two response types included in the adaptive response?

humoral and cell mediated/adaptive

what are the artificial and naturally acquired methods of active humeral immunity?

• Naturally acquired: infection, contact with pathogen

• Artificially acquired: vaccine, dead or attenuated pathogens

what are the artificial and naturally acquired methods of passive humeral immunity?

• Naturally acquired: antibodies passed from mother to fetus via placenta or to infant via milk

• Artificially acquired: injection of exogenous antibodies e.g. take blood samples from hundreds of people with that disease and inject the isolated antibodies OR milk snakes to make antivenom

what is an antigen

foreign particle present in body. illicits immune response

what are complete antigens?

Have two functional properties: -       immunogenicity: ability to stimulate specific lymphocytes to proliferate -       reactivity: ability to react with activated lymphocytes and antibodies released by immunogenic reactions

what is a hapten/incomplete antigen?

small molecules that reactivity but not immunogenicity unless attached to protein carries

what are antigenic determinants/epitopes?

• Small region of antigen that the antibody recognises. Can have lots of same or different antigenic determinants on one bacterium.

• “A group of amino acids or other chemical groups exposed on the surface of a molecule, frequently a protein, which can generate an antigenic response and bind antibody.”

what is the antibody structure

what are they 5 antibody classes?

• IgG (monomer) – most abundant

• IgM (pentamer) -  first type released in primary response

• IgA (dimer) – in bodily secretions

• IgE (monomer) – causes histamine release

• IgD (monomer) – activates B cells

what is the clonal selection of B cells referring to?

When after their first encounter with an antigen, B cells are stimulated to become either:

-       Plasma cells/effector B cells: actively secrete antibodies

memorycells: remember the specific antigen to prepare body for next exposure

what is an immune complex?

when antibody-antigen binding is occurring. Is lock and key (receptor-ligand) interaction. is specific

what is the cellular immune response/cell mediated response?

involves T lymphocytes. not antibodies

what are antigen-presenting cells (APCs) and what are the types?

• APCs - capture/process antigens for T cells, Signalling for proliferation/differentiation of lymphocytes

• types include: dendritic cells, macrophages, B lymphocytes

what are effector T cells

Are made in bone marrow, mature in thymus, have antigen-receptor interactions on cell surface. ie. they actively response to a stimulus

what do Helper T cells 1 do?

Inflammation, macrophage activation, activate cytotoxic T cells

what do helper T cells 2 do?

Mobilise eosinophils, activate B cells and antibody production

what do helper T cells 17 do?

Releases IL-17, links adaptive and innate immunity, inflammation

what do cytotoxic T cells do?

can kill certain cells, including foreign cells, cancer cells, and cells infected with a virus. Defence proteins include:

Perforins – drill holes into abnormal target cell

Granzymes – digestive enzymes that enter via holes, trigger apoptosis

Some also become memory cells

examples of autoimmune diseases?

When body can’t recognise self and the immune system attacks. e.g.

Hashimoto's thyroiditis, rheumatoid arthritis, multiple sclerosis (MS), coeliac disease (gluten), systemic lupus erythematosus (SLE), type 1 diabetes (diabetes mellitus)

what are hypersensitivities?

Body perceives threat from molecule that is harmless e.g. allergies, dust mites, pollen. Distinguished by time course and whether they involve Ab or T cells

what are regulatory T cells?

Dampen the immune response.

Two mechanisms of response:

• direct contact

• releasing inhibitory cytokines

maintains homeostasis and self tolerance and keeps immune system from overreacting