Immunity

• Antibodies are proteins produced by plasma cells that bind specifically to foreign substances (antigens) and neutralize them.
• White blood cells are able to differentiate between self and non-self to know what is part of your body and what is foreign, the body's own tissues are not destroyed 


  Why should white blood cells differentiate between self and non-self?
• What are the types of specific defence?

  Cell mediated response and humoral response
• What are the types of non-specific defence?

  Physical barrier, cilliated cells, mucus, hydrochloric acid, phagocytosis
• what cells are involved in cell-mediated response?

  T-lymphocytes
• what cells are involved in humoral response?

  B-lymphocytes
• describe phagocytosis

  the pathogen releases chemicals attracting the phagocyte, this is called chemotoxis, the receptor cells of the phagocyte binds to the pathogen, the phagocyte engulfs the pathogen forming a phagosome around the pathogen. Lysosomes in the phagocyte bind to the phagosome forming a phagolysosome which contain hydrolytic enzymes that break down the pathogen.
• what happens after the pathogen has been hydrolysed during phagocytosis?

  the soluble products are absorbed into the cytoplasm of the phagocyte
• what is cell-mediated immunity?

  the response of T-lymphocytes to foreign antigens presented on a body cell
• where are the lymphocytes made and matured?

  Both T and B-lymphocytes are made in the bone marrow, T-lymphocytes mature in the Thymus glands but the B-lymphocytes are aslo matured in the bone marrow.
• what are the stages of T cell to infection by pathogen?

  1: phagocytosis takes place

  2: pathogenic antigens are presented on the cell surface membrane

  3: receptor cells on the T-helper cell binds to the antigen on the APC which activates the T-cell.

  4: divide by mitosis and begin to differentiate

  5: the T cells stimulate other cells such as B cells and cytotoxic T-cells, the B-cells secrete antibodies, the T-cells activate macrophages(carry out further phagocytosis) and cytotoxic T-cells which destroy infected cells by releasing chemicals