B lymphocytes or B cells and T lymphocytes or T cells are the major players in adaptive immune response. In adults, these cells are derived from hematopoietic stem cells in the bone marrow. T cells mediate cell mediated immunity whereas B cells are behind antibody mediated or humoral immunity.
Learn more: Difference between B cells and T cells
T cells like B-cells originate in the bone marrow but maturation takes
place in the thymus, therefore called as T-cells. Th cells are the most
important cells responsible for overall regulation of specific immune response
(regulatory cells).
Helper T cells |
Cytotoxic T cells |
CD4 positive cells A co-receptor, CD4 surface glycoprotein is present along with T cell receptor |
CD8 positive cells A co-receptor, CD8 glycoprotein is present |
Why called Thelper cells? It "help" the activity of other
immune cells by releasing cytokines. Can activate both B cells, T cells and antigen
presenting cells like macrophages and dendritic cells |
Kills the infected cells; therefore called
cytotoxic cells (toxic to cells) Also called Killer T cells or effector cells |
Recognizes antigen bound to MHC class II
present on antigen presenting cells like B cells, macrophages or dendritic
cells |
Recognizes antigen in association with MHC class I present on all nucleated cells |
Mode of action: Activating B cells for
antibody production, secreting lymphokines that activate cytotoxic T cells
and B cells, attracting neutrophils and enhance the ability of macrophages to
engulf microbes. |
Destroys virus infected cells and tumor cells directly either by release of perforins which makes pores on cell membranes causing lysis, or granyzymes, that induces programmed cell death or apoptosis. |
Th cells are crucial for defense against
both extracellular and intracellular pathogens. |
Tc cells provide protection against
intracellular pathogens such as viruses , bacteria and parasites that
multiply in the host-cell cytoplasm |
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