The formation of stable E rosettes by human peripheral blood lymphocytes after short exposure to concanavalin A

Simultaneous increased expression of E-rosette receptor (CD2, T11) and T cell growth factor receptor on human T lymphocytes during activation

The E-rosette receptor (CD2, T11) is a differentiation antigen expressed on immature and mature human T lymphocytes. Activation of T cells from human peripheral blood with phytohemagglutinin (PHA) or with monoclonal antibody to the CD3-Ti complex (anti-Leu-4) caused the expression of CD2 to increase 10- to 20-fold. Dual parameter correlated analyses with antibody to the T cell growth factor (TCGF) receptor (anti-Tac) and anti-CD2 antibody demonstrated that the increase in CD2 expression occurred at the same time and on the same cells that expressed the TCGF receptor after stimulation with PHA. The increased expression of CD2 and the initial expression of Tac were totally inhibited by cycloheximide, but were not affected by sufficient actinomycin-D to block the T cell proliferative response. The expression of CD2 was compared with the expression of CD4 and CD8, i.e., T cell differentiation antigens on cytotoxic/suppressor or helper T cells, respectively. Although virtually all of the small percentage of freshly isolated Tac+ peripheral blood cells belonged to the CD4+, CD8- subset, both CD4+ and CD8+ T cells were equivalently activated by PHA to express Tac. By 20-30 hr after activation, the expression of CD4 or CD8 was initially decreased 10-50%. Subsequently, the expression of CD4 and CD8 returned to the levels on resting T cells but did not increase further. Therefore, the increase in CD2 expression does not reflect a universal property of cell surface antigens on activated T lymphocytes.

Induction of T-cell proliferation and enhancement of NK activity by supernatants from Con A-stimulated human peripheral blood mononuclear cells: a new lymphokine

Supernatants from human peripheral blood mononuclear cells activated by Con A contain a factor(s) that stimulates blastogenic activity of normal human peripheral blood mononuclear cells. This Con A supernatant (CAS) contains stimulatory activity for E-rosette positive lymphocytes (T cells) and requires adherent cells for stimulation of T-cell proliferation. CAS does not contain detectable amounts of IL-2 as determined by its inability to support CTLL cell growth. Nor does it contain IL-1 or interferon. Examination of functional activity of lymphocytes stimulated for 3 days by CAS revealed that NK activity is augmented. This supernate does not appear to have any direct effect on B-cell function, although it induces suppression of polyclonal PWM stimulation of immunoglobulins. Thus, CAS appears to contain a new cytokine with immunomodulating potential.

Modulation of E-receptor expression on activated T lymphocytes

Our study indicated that the newly synthesized E-receptor, as measured with 125I-labeled monoclonal anti-E receptor antibody, on activated T lymphocytes were responsible for forming stable E-rosettes at 37 degrees C. Maximum induction of new E-receptor expression required at least 50 hr of culture with polyclonal T-cell activators, phytohemagglutinin, or phorbol myristate acetate. Polyclonal B-cell activator, lipopolysaccharide were not able to induce new E-receptor expression on the surface of T lymphocytes. The expression of the new E-receptor paralleled with the induction of Tac antigen expression. Interleukins 1 and 2 or Interferon-gamma were not able to initiate the induction of new E-receptors. However, a neuropeptide, endorphin exhibited biphasic effect on modulating the E-receptor expression, in the absence of polyclonal activators. As is the case with Tac antigen expression, induction of new E-receptor antigen may be a marker for activated T lymphocytes.

Quantification of soluble E-receptor in the serum of patients with various diseases and its accompanying in vitro immunosuppression in neoplasia

Evidence in the literature indicates that soluble E-receptor in the serum may modulate T-dependent immune response. We have developed a solid-phase radioimmunoassay to measure the soluble form of E-receptor from various sources. The assay detects solubilized antigens derived from E-receptor-bearing T lymphocytes and not with non-E-receptor-bearing B lymphocytes. The sensitivity limit of the assay is 0.1 ng/ml of purified E-receptor antigen. Using this assay, one can show that the T-cell mitogen phytohaemagglutinin stimulated both lymphocytes and cells of the resting human T-cell lymphoma cell line Jurkat to shed or secrete E-receptor into the culture medium. Results of the radioimmunoassay performed on human sera indicated that some patients with Hodgkin's disease, melanoma, sarcoma, or acute or chronic lymphocytic leukaemia had elevated levels of this antigen in their serum, whereas normal human sera registered lower levels. Elevated levels of the soluble form of E-receptor in the serum were suggestive of an in vitro assessment of their immunosuppressive activity. These results indicate that activation of T-cell immunity in vivo may result in humoral immunosuppression.

The role of E receptors in the attachment of thymocytes and T lymphocytes to human target cells

Human thymocytes, activated T lymphocytes, and neuraminidase-treated T cells possess the distinct capacity of forming conjugates with various human cell lines. The present study investigated whether E receptors, which endow human T cells with their capacity to bind sheep red blood cells (SRBC), are involved in this phenomenon. Monoclonal antibodies to human T cells and various simple sugars were studied for their effect on the attachment of human T cells to target cells. A-22, a monoclonal antibody to the E receptor, inhibited the formation of E rosettes by T cells and SRBC, and reacted in immunofluorescent-staining assays with the majority of human thymocytes and peripheral T cells, and with T-cell lines capable of forming E rosettes. When human thymus cells were treated with A-22 antibody they showed a reduction of up to 70% in their capacity to attach to the GM-4762 lymphoblast cell line and the K-562 myeloid line. Antibody treatment of the target cells, rather than of the thymus cells, had no effect on the formation of conjugates between thymus cells and target cells. Treatment of thymus cells with various monoclonal antibodies to T cells which do not react with the E receptor had no inhibitory effect. The exposure of human thymus cells to various simple sugars (D-mannose, D-fucose, galactose, and lactose) markedly reduced their capacity of forming conjugates with target cells. Exposure of neuraminidase-treated peripheral blood lymphocytes and of activated T cells to A-22 antibody inhibited their attachment to human target cells. The present study suggests that E receptors play a role in the attachment of human thymus cells and activated T cells to other human cells, and raises the possibility that these T-cell receptors may be involved in the process of recognition of "self" structures by human T lymphocytes.

Defective immunoregulation in multiple sclerosis

Imbalances in T cell subpopulations have been reported in multiple sclerosis (MS). In the present study of 31 MS patients, the percentage of T cells with Fc receptors for IgG (Tg) was found to be increased in patients with chronic progressive disease, and another T cell subset binding to the Raji B lymphoid cell line was decreased. An inverse correlation (r = -0.675; < 95% confidence limit) was found between these two subsets, suggesting that they vary inversely in MS. The mitogenic responses of MS mononuclear cells, isolated T cells, and recombinet T and non-T cells to the lectins phytohemagglutinin and pokeweek mitogen (PWM) did not differ from those of normal cells. However, more immunoglobulin (Ig)-producing cells were generated in a PWM-driven system with cells from MS patients than with cells from age-matched controls (p < 0.05). Autologous recombination of separated T and non-T cells did not significantly modify these results. T cells from MS patients added to B cells from normal controls exerted an effect that was related to their percentage of Tg cells; that is, values above 15% were associated with a suppression of Ig production, whereas for Tg values below 12%, a helper effect or no modification was observed. These results suggest that changes in T cell subsets in MS are related to changes in functional ability to modulate Ig production by normal B cells. However, MS B cells partly escape regulation by their own T cells, suggesting an associated B cell hyperactivity.