Adaptive Immunity

Question 1

How do B-cells recognise antigens?

Answer 1

• Variable region provides antigen receptor specificty
• Activation of B-cell: B-cell binds to antigen receptor
Produces cells that secrete antibodies/
immunoglobulin
Antibodies same shape as B-cells antigen
receptor
They provide fit for specific epitope

Question 2

How do T-cells recognise antigens?

Answer 2

• T-cells bind to antigen fragments on host cells
• Antigen fragments joined to Major histocompatibility molecules
• MHC molecules bind to and transport antigen fragment to cell surface: antigen presentation
• Process necessary for T-cells to participate in adaptive immunity

Question 3

How do helper T-cells activate adaptive immunity?

Answer 3

• Foreign molecule binds to antigen fragment on the helper T-cells
• Antigen is displayed on the antigen presenting cell (APC)
• APC have class 1 & 2 MHC molecules on the surface
• Class II MHC provides molecular signature by which APCs are recognised
• Antigen receptors on Helper T-cells surface binds to antigen and class II MHC
• Cytokines signal exchange between antigen and helper T-cells
• Helper T-cell stimulated to produce own cytokines

Question 4

How do antigens trigger adaptive immunity?

Answer 4

• Antigens elicit response from T and B cells
• Cells bind to antigen via antigen receptors
• Immune system produces millions different antigen receptors
• Antigens either proteins, polysaccharides, toxins secreted by bacteria
• Antigen binds to antigen receptor by epitope
• Cells made to recognise specific molecule