Unit 5

Immunity refers to protection from infectious disease

==Insuficient== immune activity results in infections

==Overactivity== results in hypersensitivity, allergies and rejection of transplanted organs

Clonal Selection Hypothesis is when foreign antigens are recognised but not self-antigen

Clonal expansion of ==TH0== is driven by ==autocrine cytokine IL-2==

1.^^APC^^ take up antigens to the site of infection

2.Present antigens on ^^MHC Class II Molecules^^

3.Move to secondary lymph nodes and present to ^^helper T cells^^

4.Helper T cells ^^recognise^^ the antigens of MHC Class II Molecules through TCR providing ^^signal^^ 1

5^^.BD7^^ molecules on APC molecules interact with ^^CD28^^ molecules providing ^^Signal II^^ which activates CD4 T cells

With only signal 1 this results in anergy of T cells ^^( avoids immune response of self antigens)^^
]]Signal 1 + 2 results in Helper T cells being activated increasing calcium levels Calciuerin levels]]
Calciuerin causes transcription factors NFATs transcription of IL-1 and IL-2 receptor genes
Autocrine action of IL-1 and IL-2 cause ^^profileration of helper T cells^^
Calciuerin and mTOR target this pathway MOA of immunosupressant drugs
Th0 cells then differentiate in to Th1, Th2, Th17 or Treg cells which designed to \n have effector responses in the line of cell-mediated responses
^^Polarisation of T cells^^ is driven by inate response