Controversy exists as to the functional capacity of T lymphocytes in patients with B-cell chronic lymphocytic leukemia (CLL). We have used a limiting dilution (LD) culture approach to quantitatively assess frequencies of proliferating lymphocyte precursors (PLP), cytotoxic lymphocyte precursors (CLP), and interleukin-2 (IL-2)-producing helper lymphocyte precursors (HLP). Unseparated mononuclear...

Murine T lymphocytes sensitized in vitro against either allogeneic lymphocytes or syngeneic hapten-conjugated lymphocytes do differentiate into highly effective cytotoxic T lymphocytes (CTL) (1-3). In vivo immunization of T lymphocytes to the same antigens, however, results in the generation of only marginal cytotoxic activity (1,4,5). Recently we found that the weakness of in vivo generated cy...

The initiation of immune responses usually requires interactions of T lymphocytes with antigen-presenting cells. The specificity of these interactions depends on the recognition by the T cell’s antigen receptor of an antigenic peptide presented in a complex with molecules of the major histocompatibility complex (MHC). But a successful immune response requires additional costimulation of the T c...

Ligation of cytotoxic T lymphocyte antigen 4 (CTLA4) appears to inhibit T cell responses. Four mechanisms have been proposed to explain the inhibitory activity of CTLA4: competition for B7-1 and B7-2 binding by CD28; sequestration of signaling molecules away from CD28 via endocytosis; delivery of a signal that antagonizes a CD28 signal; and delivery of a signal that antagonizes a T cell recepto...

cytotoxic in spite of lacking the costimulatory receptor CD28, which is crucial for optimal T cell function. The mechanisms that govern CD4 CD28 T cell function are unknown. Objective: Our aim was to investigate the expression and role of alternative costimulatory receptors in CD4 CD28 T cells in ACS. Methods and Results: Expression of alternative costimulatory receptors (inducible costimulator...