14.2 Flashcards
What is required for an antigen to trigger an immune response?
-Antigens must be on antigen presenting cells(APC) like B cells, macrophages and more.
-Antigen bound to other major histocompatibility complex molecules (MHC), allow antigen to displayed on cell surface
Similarity/Difference between CD4+ and CD8+
Similarity: Both types of T-cells
Differences:
CD4+
- recognizable by MHC class II proteins
-coordinate immune response
CD8+
- kill cells that display antigens on surface, recognizable by MHC class I
What is the relationship between t cells and thymocytes?
Thymocytes are immature T cells that are produced in the bone marrow and then migrate to the thymus gland to mature into functional T cells. Once they mature, they are called T cells.
Some thymocytes express both the CD4 and CD8 proteins.
These double-positive cells have the ability to interact with both MHC class I and MHC class II molecules. However, depending on which MHC molecule they interact with more effectively, they will undergo a process of selection and maturation. Either CD4[activating other immune cells.] or CD8[ killing the infected cells]
What does MHC mean?
present antigens to T cells. MHC molecules are found on the surface of cells and they bind to antigens, which are fragments of proteins from pathogens or abnormal cells. By presenting these antigens, MHC molecules signal to the immune system that a cell is infected or abnormal. This allows T cells to recognize and respond to the antigens, either by activating other immune cells or by directly killing the infected or abnormal cells. MHC membrane. These antigens are used by the immune system to distinguish between self and non-self cells.
MHC genes are often referred to as ___ because they were first identified in __
human leukocyte antigen (HLA) genes, leukocytes
Professional antigen-presenting cells (APCs).
-Include dendritic cells, macrophages, and B cells.
-When they encounter antigen, break it down on fragments and display on surface using MHC class II, then helper T cells can bind initiating immune response
Difference between MHC II and I
MHC I molecules present antigens derived from intracellular pathogens (such as viruses) to cytotoxic T cells. MHC II molecules present antigens derived from extracellular pathogens to helper T cells.
How are transplants related to MHC antigens?
MHC antigens found on surface of cells and helps immune distinguish self from other. During a transplant if MHC antigens are too different from one’s own, reject transplant.
CD4 (on a helper T cell) docks to an APC’s MHC class II molecule. Binding of the helper T cells promotes secretion ___
which stimulate proliferation of helper T cells. The helper T cells secrete more to initiate both the
of cytokines by the APC;
humoral response (secretion of antibodies by plasma cells and the CMI (attack on
infected cells)
What is so interesting about cytotoxic T lymphocytes (CTLs)?
They express CD8+ receptors and T cell receptors (TCR). CD8 binds to MHC I, if TCR matches epitope of MCH I, cell death.
In other words, the CTL recognizes and kills cells that display a specific antigen on their surface.
MHC class I molecules occur on all nucleated cells . WHat about MHC class II?
they don’t
Profession APC
-dendritic cells, macrophages, B cells
-can present antigens to activate T cells
-both MHC I/ II
-foreign antigens to
-present foreign antigens to helper T cells
What is special about Virus-infected cells (or cancer cells) ?
This means that when a body cell becomes infected with a virus or becomes cancerous, it can display fragments of the virus or cancer cells on its surface. These fragments are called antigens. Cytotoxic T cells, which are a type of immune cell, can recognize these antigens and destroy the infected or cancerous cell.
Helper T cells- have
Cytotoxic T Cells- have
CD4, important for B and T cell growth and activation
CD8,Kills specific cells
