Initial response to infections = non-specific so next phase = specific response that confers immunity.
Immunity = ability of organsims to resist infectino by protecting against disease-causing microorganisms.
An antigen = any part of organism or substance that is recognised as non-self by immune system, stimulating an immune response.
Antigens = usually proteins part of cell-surface membrane or cell walls or invading cells e.g. on microorgansims or diseased cells.
Precense of antigen triggers antibody production as part of body's defence system.
Phagocytosis is a non-specific immune response (occurs whatever the infection)
Specific responses react to individual forms of infections - slower in action but can provide long-term immunity - depend on type of white blood cell = lymphocyte.
Two types of lymphocyte:
- B lymphocytes (B cells) = associated with humoural immunity (involving antibodies present in body fluids), respond to bacteria and viruses.
- T lymphocytes (T cells) = associated with cell-mediated immunity (involving body cells), respond to own cells altered by viruses or cancer and transplanted tissues.
Both types of lymphocyte made in bone marrow, but T mature in the Thymus…