T Cells in Infection Flashcards
What are the differences between cell mediated and humoral immunity?
Humoral: Product of B lymphocytes, involves antibodies, effective against extracellular antigens (viruses, toxins, extracellular bacteria)
Cell mediated: Product of T lymphocytes, does not involve antibodies, effective against intracellular antigens (virus-infected cells, tumour cells, transplanted organs)
How do receptors on T cells vary?
All present CD3 and TCR
Helper T cells present CD4
Cytotoxic T cells present CD8
Regulator T cells present CD45RB
What are the three responses of T cells?
Cytotoxic responses (ability to kill cells) Helper responses (assist other cells in responding) Regulator responses (inhibitory cytokines)
What is the major histocompatibility complex and what are its classes?
Class 1 : surface structures found on all nucleated cells and present to CD8 T cells
Class 2: surface structures found on specialised antigen-presenting cells and B cells. Present antigenic peptides to CD4 T cells
How does antigen presentation differ in terms of class 1 and class 2 MHC structures?
MHC 1 usually comes from a virus infected cell. The virus is replicated within the cells and presented.
MHC 2 usually comes from phagocytosed antigenic material which is broken down and then a fragment is presented
How are T lymphocytes activated?
An antigen is bound to the specific receptor (MHC 1 or MHC 2) on a cell which the T cell binds to. Cytokines from a helper T cell activate this T cell, which then proliferates and differentiates into memory cells and helper/cytotoxic T cells
What are the functions of cytokines (interleukins)?
Regulate the quality, amplitude and duration of immune and inflammatory reactions
What are some problems with immunity?
Over reactivity to innocuous substances (allergy)
Immune-mediated tissue damage (rheumatic fever)
Immune destruction by infectious agent (aids)
Autoimmunity (treat self as non-self eg. pernicious anaemia)
