4. Explain the roles of B-cells, MHC proteins, helper T-cells, cytotoxic T-cells, memory cells and immunoglobines in the antigen/body response.
B cell: a type of lymphocyte normally involved in the production of antibodies to combat infection. It is a precursor to a plasma cell. During infections, individual b-cell clones multiply and are transformed into plasma cells, which produce large amounts of antibodies against aparticular antigen on a foreign microbe. This transformation occurs throughinteraction with the appropriate cd4 t helper cells. Lymphocytes that are capable of producing antibodies in response to detecting the presence of aparticular [[antigen.
MHC molecules typically interact with the cell surface receptor of a type of lymphocytes known as killer T cells. The receptor on the killer T cell binds to the MHC molecule and informs the killer T cell on whether that cell is normal or not. The interesting part of the story is how the T cell can distinguish the MHC class I protein on a normal cell from that on an abnormal one. The key concept here is to appreciate that the MHC molecule has within its structure a groove. Into this groove is bound a small piece of protein derived from within the cell, that was placed there during the synthesis of the MHC molecule. If this peptide of 8 or 9 amino acids happens to be a foreign peptide, such as one produced by a viral gene, or a cancer gene, the T cell will become activated, and attack the infected or cancerous cell. Of course there many more details involved in this process. Of primary interest to medicine and the average person is the fact that when an organ is transplanted between non-identical people, it is the recipient's T cells reacting against the donor organ MHC (Major Histocompatibility Complex) proteins that causes much of organ rejection.
Helper T: This type of T lymphocyte releases lymphokines upon stimulation of specificantigens to promote the activation of B lymphocytes as well as killer T lymphocytes.
Cytotoxic T-cell: lymphocyte-like effector cells which mediate antibody-dependent cell cytotoxicity. They kill antibody-coated target cells which they bind with their fc receptors.
Memory T- cell: The long lasting immune memory is humoral and resides in b-cells, although it appears that persistence of the antigen may be essential. T-cell memory is shorter. A type of [[lymphocyte that is released as a [[specific immune response that is stored in case the specific [[ antigen attacks once again. Live vaccinations are used to initiate the production of [[memory cells.
Immunoglobin: (1) Any of several classes of structurally related proteins in the blood serum, produced by plasma cells as an immune response against foreign agents (antigens).
(2) The fraction of the blood serum containing antibodies.