Activation of human B and T lymphocytes by protein A of Staphylococcus aureus

Abstract

Protein A from Staphylococcus aureus, in soluble form or coupled to Sepharose beads, acts as a polyclonal B cell activator (PBA) for human lymphocytes in blood and spleen. PBA activity was demonstrated in spleen cells by the ability of protein A to induce the formation of intracellular immunoglobulin synthesis and to activate polyclonal antibody secretion demonstrated against fluorescein isothiocyanate-coupled sheep erythrocytes in a modified hemolysis in gel assay. More plaqueforming cells (PFC) were seen in unseparated cells than in purified B cells. In blood lymphocytes, only few PFC were activated by soluble protein A. Protein A increased DNA synthesis in blood and spleen cells. At a concentration of 100 microgram/ml the peak response was on day 4 or 5, but at 1 microgram/ml the peak response occurred later. On day 4 of culture, high mitogenic activity was seen in unseparated lymphocytes or mixtures of separated B and T cells, whereas in enriched B and T cell suspensions activity was low. On day 7, however, DNA synthesis in both the enriched B and T cells was higher than in mixtures of B and T cells. Protein A stimulated DNA synthesis in thymus cells with a peak response on day 6. It is concluded that protein A alone or as an IgG complex can activate both B and T cells, though the mechanism of activation is not known and may be different for B and T cells.

Immunomodulatory effects of human foetal liver-derived mesenchymal stem cells

“…PHA activates T cells, 17 SpA activates T-and B-cells. 18 Less suppression occurred after activation with the T-cell mitogen ConA 17 and PWM, which induces T-cell dependent B-cell stimulation. 23 This discrepancy of fMSC with an ability to suppress lymphocyte proliferation induced by mitogens but not the polyclonal, polyepitope MLC could be because of immunologic immaturity during the end of the first trimester.…”

“…15360-019). 17,18 These were added to one population of 1.5 Â 10 5 lymphocytes supplemented with 1500, 15 000 or 30 000 irradiated MSCs and cultured, as described above for the MLC method.…”

Mesenchymal stem cells are susceptible to human herpesviruses, but viral DNA cannot be detected in the healthy seropositive individual

“…Peripheral blood lymphocytes were stimulated with antigen; final concentrations were 10 mg/ml staphylococcal aureus protein A (SpA) (Pharmacia, Uppsala, Sweden), HSV-1/1000 (SMI, Solna, Sweden), VZV 1/1000 (SMI), CMV 0.5 mg/ml (Biosite, Ta¨by, Sweden) and candida mannan (CM) 100 mg/ml (gift from Dr Lena Klingspor, Laboratory of Clinical Bacteriology, Karolinska University Hospital Huddinge, Sweden). [28][29][30] The plate was incubated for 6 days.…”

Mitogenic Activity of Cytoplasmic Membranes Isolated from L‐Forms of Staphylococcus aureus

“…With mitogens of S. aureus other than cell walls, Forsgren et al (18) found that protein A of S. aureus is mitogenic for human B lymphocytes, but not for T-cells, whereas Ringden and Rynnel-Dagoo (32) showed that protein A of S. aureus stimu- lates not only human B lymphocytes but also T cell to proliferate . Forsgren (16) demonstrated that protein A is produced by L-forms of S. aureus, although its concentration detectable in the culture supernatant of L-forms was far less than that of the corresponding bacterial forms .…”