T Lymphocytes & Cell-mediated Immunity

What are the 2 types of lymphocytes?

T lymphocytes or T cells and B lymphocytes or B cells

What are T lymphocytes (T cells)?

T cells mature in the thymus gland, involved in cellular response where they respond to antigens presented on body cells

What are B lymphocytes (B cells)?

B cells mature in the bone marrow, involved in the humoral response where they produce antibodies found in body fluids (or humors)

What are T helper cells?

These cells have receptors on their cell-surface that bind to complementary antigens on antigen-presenting-cells (APCs). After binding, they can form memory cells, stimulate B cells or phagocytes and activate cytotoxic T cells.

What are the stages of the cell mediated response?

1. Helper T cells with complementary receptors bind to antigens on APCs- Helper T cells do not recognise antigen unless it is on an APC, T helper cells are now activated

2. Activated T- helper cells divide by mitosis to form genetically identical clones (via clonal selection)

3. They also secrete chemicals which activate other T cells and B cells which have the same receptors:

   • stimulate cytotoxic T cells- produce chemicals that make APC’s membrane permeable, which can kill the cell- holes allow toxins to invade, which will definitely kill the cell end everything in it

   • Stimulates B lymphocytes cells…

   • Stimulates phagocytosis by increasing phagocyte production

What else do T cells form?

Forms T memory cells- circulate in body to provide long term immunity to a certain virus