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Biology Articles » Immunobiology » Interactions Between Natural Killer Cells, Cortisol and Prolactin in Malaria During Pregnancy » Characterization of NK Cells

Characterization of NK Cells
- Interactions Between Natural Killer Cells, Cortisol and Prolactin in Malaria During Pregnancy

NK cells are large granular lymphocytes that comprise approximately 5% to 15% of peripheral blood mononuclear cells (PBMC) and 5% to 10% of lymph nodes. NK cells were first identified by their ability to lyse tumor cells without prior immunization. Actually, NK cells are defined as lymphocytes lacking the T cell receptor (TCR) complex and are CD3 negative. The best surface antigen to identify human NK cells is the neural cell adhesion molecule (CD56) first identified in brain tissue.5 Although CD56 may have adhesion function in neural tissue based on homotypic interactions,6 its function in NK cells remains unknown. Monoclonal antibodies to several other antigens can be used to identify important subsets of NK cells. CD16 (FcγRIII) is the Fc receptor expressed on the surface of CD56+dim NK cells that identifies the most mature cell population belonging to this lineage. Well-characterized unique NK cell subsets circulating in peripheral blood are CD56+bright NK cells7 that are minimally cytotoxic8 and highly proliferative.8,9 CD56+bright NK cells constitutively express interleukin (IL)-2 receptor and lack FcγRIII.10 They also express c-kit11 and the receptor for T cell factor-1 (TCF-1).12 The CD56+dim NK cells can be divided into subpopulations based upon CD2 expression. CD2 is the ligand for lymphocyte function-associated antigen-3 (LFA-3, or CD58). All NK cells express the lymphocyte marker CD7.13 CD8, also present on the cytotoxic population of T-cells, is expressed by approximately 35% of CD56+dim NK cells.9 In contrast to CD8+ T cells, where CD8 is composed of both α and β chains, CD8 expressed on the surface of NK cells is composed of predominantly CD8-α chains.14


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