Cell mediated immunity is a defense mechanism primarily handled by lymphocytes and does not involve antibodies, targeting infections from viruses, fungi, and certain bacteria. This process includes the recognition of antigens by T cells and is vital for eliminating intracellular pathogens and tumor cells. It starts with antigen-presenting cells like macrophages that display antigens to T cells, leading to a coordinated immune response.

1. CELL MEDIATED
IMMUNITY
Name- GarimaThakur
M.Sc Zoology 1

2. Cell mediated immunity
■ Cell mediated immunity is defined as the immunity developed by cell mediated
response.
■ It is also called as cellular immunity orT cell immunity.
■ Cell mediated immunity does not involve antibodies.
■ It is the major defence mechanism against infections by viruses, fungi, and few
bacteria like tubercle bacillis.
■ It is also responsible for delayed all allergic reaction and the rejection of transplanted
tissues.

3. ■ Cell mediated immunity is offered byT lymphocytes and it starts developing whenT
cells come in contact with the antigens.
■ Usually the invading microbial and non microbial organisms carry the antigenic
materials.
■ These antigenic materials are released from invading organisms and are presented to
the helperT cells by antigen- presenting cells.
■ T cell recognise foreign antigens on the surface of cells, organisms, or tissue:
1. HelperT cell
2. CytotoxicT cells
■ T cells regulate proliferation and activity of other cells of the immune system : B cells,
macrophages, neutrophil, etc.

4. ■ Primary function of cell mediated response-
1. Eliminate intracellular pathogens.
2. Eliminate tumor cells.
■ Both Ag specific and non specific cells are involved-
1. Ag specific:CD8+Cells.
2. Non specific: macrophages, neutrophils, and natural killer cells.
■ Both specific and non specific require cytokines.

5. ■ In the Cell mediated immunityT cell plays one of the important role for the process of
crosstalk with other immune system as well as to signal B cells to produce the
antibody mediated immune response.
■ Now, cell mediated immunity starts with the macrophages i.e. a dendritic cells those
are antigen presenting cells.They not only engulf the antigen they also break them
down and show them toT cells. NowT cells with the help ofT cell receptor it interact
with the major histocompatibility complex 2. It receives signal from MHC 2 because
MHC 2 is attached with the antigen that is showcased by the macrophage.