Anti-CD2 Antibody [LT2] (FITC) (A86566)

Most lymphoblastic lymphomas (LBLs) are regarded as neoplasms of immature T cells because they express cytoplasmic CD3 and frequently carry T-cell receptor (TCR) gene rearrangements. Immature natural killer (NK) and T cells, however, have a common bipotent T/NK-cell precursor in the thymus, and NK cells also express cytoplasmic CD3. Thus, some LBLs could arise from immature NK cells. Mature NK cells express 2 CD94 transcripts: 1A, induced by interleukin 15 (IL-15), and 1B constitutively. Because immature NK cells require IL-15 for development, CD94 1A transcripts could be a marker of NK-LBL. To test this hypothesis, we used laser capture microdissection to isolate IL-15 receptor alpha(+) lymphoid cells from the thymus and showed that these cells contained CD94 1A transcripts. We then assessed for CD94 transcripts in 21 cases of LBL that were cytoplasmic CD3(+), nuclear terminal deoxynucleotidyl transferase positive (TdT(+)), and CD56(-), consistent with either the T-cell or NK-cell lineage. We found that 7 LBLs expressed CD94 1A transcripts without TCR gene rearrangements, suggesting NK-cell lineage. Patients with NK-LBL were younger than patients with T-LBL (15 years versus 33 years; P = .11) and had a better 2-year survival (100% versus 27%; P < .01). These results improve the current classification of LBL and contribute to our understanding of NK-cell differentiation.

In the rat, monoclonal antibodies (mAbs) against the T-lymphocyte receptor (TCR), CD3 antigen and CD2 antigen are mitogenic for T lymphocytes. Antibodies against CD43 (leukosialin) and CD5 are not, but can enhance the effects of other stimuli. Activation of a T-lymphocyte cell line in terms of triggering an increase in free cytoplasmic Ca2+ [( Ca2+]i) was mediated by mAbs against Class 1 MHC and CD4 in addition to the mitogenic mAbs. In the presence of non-activating levels of anti-TCR mAb a strong synergistic signal was seen with anti-CD4, but incubation with anti-CD4 prior to activation with anti-CD3 inhibited the CD3 signal. Stimulation of DNA synthesis in resting T cells via anti-CD2 mAbs required a combination of two non-competitive antibodies and addition of a third anti-CD2 mAb inhibited the activation. The anti-CD2 mAbs were active on all types of mature T cells from peripheral lymphoid organs and the thymus, but cells in the thymus that lacked a TCR could not be activated via CD2. Rat CD2 was transfected into Jurkat cells and cross-linking with anti-rat CD2 mAbs gave an increase in [Ca2+]i similar to that seen with an anti-human CD3 mAb. All three types of anti-rat CD2 mAbs gave a signal including the mAb that inhibited mitogenesis. Signal transduction via CD2 was not seen in L cells and was only weakly observed in TCR-ve Jurkat cells that had been transfected with rat CD2. The cytoplasmic domain of transfected CD2 was shown to be important for the signal transduction since no increase in [Ca2+]i could be triggered in cells expressing mutant CD2 that lacked the cytoplasmic domain. Mutant forms with increasing lengths of cytoplasmic domain showed functions that progressively approached that of the native function.