Spontaneous release of the Leu-2 (T8) molecule from human T cells.

Abstract

Sensitive enzyme-linked immunosorbent assays (ELISA) for the detection of human T cell antigens in soluble form have been developed. The assays use mouse monoclonal antibodies and specific anti-Leu sera prepared in rabbits by immunizing with Leu antigens absorbed to monoclonal antibody affinity columns. With these assays, Leu-1, -2, and -3 antigen signals from extracts of as few as 5 X 10(3) cells could be detected. When culture supernatants from various cell lines were tested, Leu-2 antigen, but not Leu-1 or Leu-3, was found to be present. Leu-2 antigen was present only in supernatants from T cell lines that expressed Leu-2 on their cell surface. Leu-2 antigen accumulated progressively in the supernatant of low density culture and its presence did not depend on cell proliferation or on fetal calf serum in the culture medium. The Leu-2 antigen in the supernatant was found to have only one Leu-2a determinant, whereas Leu-2 antigen from cell extracts had at least two determinants. The Leu-2 molecule was effectively purified from supernatant with an anti-Leu-2a affinity column. The purified Leu-2 antigen from supernatant of HPB-ALL cells was a single polypeptide chain of 27,000 mol wt, whereas Leu-2 antigen present on HPB-ALL cell surface was composed of two or more identical polypeptide chains of 33,000 mol wt linked by disulfide bonds. Normal human sera and sera from leukemia patients were also examined for the presence of the Leu-2 antigen. Normal human sera contained low levels of Leu-2 antigen but sera from Leu-2-positive leukemia patients had high levels. These results indicate that Leu-2 antigen is released from human T cells under physiological conditions.

Serum cytokine profiles in experimental human malaria. Relationship to protection and disease course after challenge.

“…Supernatants of CD8+ human cell lines contain high levels of soluble, shortened CD8 (sCD8) (39). The release of sCD8 is increased upon stimulation in vitro (39) and it is present in high concentrations in sera from patients with various malignant, autoimmune, and infectious processes (39,45,63). The results presented here show a gradual increase in sCD8 concentrations in nonprotected volunteers, reaching peak concentrations at the time of the development of fever and with concordant magnitude.…”

Activation of T lymphocytes in dengue virus infections. High levels of soluble interleukin 2 receptor, soluble CD4, soluble CD8, interleukin 2, and interferon-gamma in sera of children with dengue.

“…(18)(19)(20) and IFNy (18,20), and release sIL-2R (21). Activated CD8' T lymphocyte release sCD8 (22,23), while activated CD4' T lymphocytes release sCD4 (Susan Kline, personal communication). We previously reported that dengue virus-specific CD4' CD8-memory T cells are induced by dengue virus infections (10).…”

Assay for the Soluble Interleukin-2 Receptor by Sandwich Enzyme Linked Immunosorbent Assay

“…When HRP-labeled anti-IL-2R antibody or anti -human IgM antibody was added, the respective antibody bound specifically with soluble IL -2R or human IgM (Table II). Receptor shedding is seen in cell surface receptors , such as the insulin receptor (18), epidermal growth factor receptor (19) and CD8 (20) , if a cell-free receptor retains good affinity , it could mediate the down regulation of the cellular response to the ligand. Elevation of the soluble IL-2R level in serum may be a common phenomenon in a disease induced by an immunological mechanism .…”