Vaccines

Non-specific defences

Physical barriers, chemical secretions, inflammatory response, phagocytes and natural killer cells

Example of a physical defence

Epithelial tissue - blocks the entry of parasites

Example of chemical secretions

Hydrolytic enzymes in mucus, saliva and tears destroy bacterial cell walls; low pH environments of the secretions of stomach, vagina and sweat glands denatures cellular proteins of pathogens

Effect of the inflammatory response

Injured cells release signalling molecules that results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes

Action of phagocytes in the non-specific response

Kill parasites using powerful enzymes contained in lysosomes; the phagocytes engulf pathogens and store them inside a vacuole in the process of phagocytosis

Role of Natural Killer cells

NK cells identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis.

Specific cellular defences involves...

a range of white blood cells constantly circulating in the bloodstream monitoring tissues

What is released if tissues become damaged or invaded?

Cytokines

Consequence of cytokine release

increased blood flow, resulting in non-specific and specific white blood cells accumulating at the site of infection or tissue damage

What type of blood cell has a receptor on its surface to recognise parasite antigens?

Lymphocyte

Clonal selection

The process by which a lymphocyte is selected and divided following binding of an antigen to a lymphocyte

Two impacts of lymphocyte activation

production of antibodies by B lymphocytes; induction of apoptosis in parasite-infected cells by T lymphocytes

Variable region of an antibody

region of an antibody where the amino acid sequence varies greatly between different antibodies. Gives the antibody specificity for binding antigen

What happens when the antigen binds to the variable region of an antibody?

An antigen-antibody complex is formed - this can inactivate the parasite, rendering it susceptible to phagocytosis or cell lysis

Memory lymphocyte cells

Following initial antigen exposure, memory lymphocyte cells are produced for that antigen. This results in an amplified and rapid antibody production if secondary exposure to the same antigen occurs.