Cell Mediated Immunity 1 Flashcards
How can T cells be distinguished?
The expression of TCR and associated CD3 complex
How are T cells categorised?
The expression of CD4 (t helper cells) or CD8 (cytotoxic)
What comprises of a TCR?
An Alpha and Beta chain with variable regions and constant domains close to the cell membrane, the alpha/beta chains is surrounded by signal transduction molecules which form CD3 complex, Next to CD3 complex is either CD4 or 8
What is the difference in structure between CD4 and CD8 molecules?
CD4 molecules consist of a single elongate chain
CD8 molecules consist of two shorter alpha and beta chains or two alpha
What is a homodimer and heterodimer?
Homodimer- restricted to recognising antigens in MHC complex
Heterodimer- can recognise free antigens
How is diversity in antigens achieved in B/T cells?
Somatic recombination
What are the two forms of T cell receptors?
alpha/beta homodimers, gamma/delta heterodimers
Describe the basic structure of B cell receptors
Constant and variable regions with heavy and light chains with transmembrane region
Outline the process of T cell selection in thymus
1- immature T cells enter thymus core from the bone marrow
2- Induced to express TCR with both CD4/8
3- Thymocyte determines if TCR functional with testing against MHC class II or I expressed by cortical epithelial cell (positive selection)
4- Cells that don’t carry functional receptors die by apoptosis
5- Thymocytes test for high affinity for self-peptide expressed by MCH on thymus dendritic cell (negative selection)
6- Cells with self receptors die by apoptosis
7- Within the medulla the thymocyte expresses either CD4/8 depending on whether it encountered MHC I or II
What does MHC stand for?
Major histocompatibility complex
Describe the structure of MHC class I and II
MHC I- one long alpha chain with three globular domains paired with a short beta 2 micro globulin
MHC II- One alpha and beta chain each having two globular domains
What cells are MHC class I expressed on?
All nucleated cells of the body
Where is MCH class II expressed?
Normally immune cells (macrophages, dendrites, lymphocytes, inducive on certain epithelial and stroll cells
Which cells have the ability to process and present antigens?
Dendrites, Macrophages, B cells, Maybe Basophils
What are the three types of antigen presenting cells?
Professional, non-professional and induced
