CD28
CD28 was identified in early 1980s by Martin and colleagues by monoclonal antibodies recognizing a 44 kDa protein on the surface of human T lymphocytes (Martin et al. 1980). Further experiments from Gmunder and Lessener evidenced the crucial role of this molecule in costimulating T cell responses by synergizing with PHA in inducing T cell proliferation (Gmunder and Lesslauer 1984).