(Science: immunology) glycoprotein members of the immunoglobulin superfamily which participate in t-cell adhesion and activation. They are expressed on most peripheral t-lymphocytes, natural killer cells, and thymocytes, and function as co-receptors or accessory molecules in the t-cell receptor complex.
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... - T-cells that bring CD4 on their membrane, they are called as CD4+ T cell, will recognize only cells that express MHC classII on their membrane - CD28 will interact only with B7 (protein molecule of the macrophage) etc. Also it can be used to distinguish such lymphocyte from different clones. ...
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