Immune System - Paper 2000/1999

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2000_2^nd semester_Q3_Part_B 

Antibody:

v     Secreted by plasma cells, daughters of b lymphocytes, in humoral immune response

v     Are made of two polypeptide chains (a light and heavy chain) with two binding sites for antigen per antibody

v     The stem of the antibody is recognised by the body’s cells so that they know which ones to engulf after the formation of antigen-antibody complex

v     Several classes of antibodies exist namely: IgM, IgA, IgD, IgG, IgE, with each having the same antigenic specificity but used in different circumstances

v     Can be given to a person passively or actively to induce a humoral immune response

Cytotoxic T lymphocytes:

v     Are effector cells of cell mediated immunity

v     Can directly attack antigens by involving in direct close cell to cell contact

v     Co-stimulated by the release of cytokines and proliferation of t helper cells

v     Circulate in blood, lymph and connective tissues of the body

Immunological Memory

v     Concept to describe the immune response the second time the same antigen enters the body

v     Caused by the presence of b memory cells (humoral immunity) and t memory cells (cell mediated immunity)

v     Second response to an antigen is faster, prolonged, more destructive because b memory cells already have receptors specific to that antigen. This is the same case with t memory cells too.

v     Draw a diagram explaining the nature of a first and second response

v     Concept on which vaccinations are based on

 Chemotaxis

v     Involved in attraction of phagocytes to areas of tissue damage and inflammation

 1999_2^nd semester_Q3_Part_B

 Antigen presenting cells

v     Involved in both humoral and cell mediated immunity

v     Have special MHC-II proteins on cell membranes which act to bind to haptens of the antigen

v     Engulf the antigens and partially digest the, leaving the antigenic portion to stick out of the cell membrane

v     Can be macrophages, b lymphocytes, neutrophils or other dendritic cells

v     Main function is to present the hapten-antigen complex to the helper t cells, so that a further complex can be formed causing stimulation of b or t cells (depending on types of immunity).

 Helper t cells

v     Involved in both cell and humoral immunity

v     Have specific receptors for the hapten

v     Bind to the hapten-MHC-II protein complex and cause co-stimulation and also release of cytokines

v     Induce the stimulation/activation of b lymphocytes and Cytotoxic t cells

 MALT

v     A type of diffuse lymphoid tissue

v     Contains many lymphocytes which circulate looking for antigenic material present

v     Different body areas contain MALT – i.e.: GALT etc

v     The epithelium and underlying connective tissue contains the lymphocytes that can contain concentrated regions of lymphocytes called nodules, or they can be diffused around the tissues.

 Immunological Memory

v     See exam answer above ^