Plaque-forming cells in man. II. Evidence of the existence of active suppressor cells in peripheral blood of normal plaque-forming cell non-responders

A myelopeptide from unstimulated bone marrow cells with immunomodulatory activity in lymphocyte cultures from healthy donors and patients with hypogammaglobulinemia and active lupus erythematosus

A myelopeptide (SAP) was derived from culture supernatants of unstimulated animal bone marrow. SAP consists of a group of peptides with a molecular weight of about 2000 D, having a broad variety of biological activities. Testing immunoregulatory properties of the purified factor Petrov, Mickhailova & Zacharova [(1971). Immunoglobin synthesis in syngenic cells of different lymphoid tissues. J. Immun., 106 1086-1089] found enhanced antibody production in mice (SAP-stimulator of antibody production). We show here that the substance could induce expression of activation markers on human lymphocytes (4F2, HLA-class II antigens, thermostable SE rosette formation) and potentiate their appearance in combination with mitogens (PWM, PHA, Con A). Although SAP was not mitogenic for itself, it enhanced lectin-induced 3H-thymidine incorporation and T-cell-dependent B-cell differentiation in a dose-dependent manner. The factor was able to reconstitute disturbed PWM-driven Ig synthesis in lymphocyte cultures derived from two patients with hypogammaglobulinemia and a healthy non-responder to PWM. On the other side, SAP potentiated the inhibitory activity of PWM on elevated spontaneous IgG secretion in cultures derived from patients with active SLE. Findings of this study indicate immunomodulatory capacity of SAP on human peripheral blood lymphocytes possible via T-cell activation. The results suggest a potential therapeutic application of SAP in patients with disturbances in the T-dependent B-cell differentiation.

Polyclonal induction of immunoglobulin synthesis by feline leukocytes as identified in a reverse hemolytic plaque assay

Optimal conditions of culture and assay for identification of feline immunoglobulin-secreting mononuclear cells were determined for the staphylococcal protein A-reverse hemolytic plaque assay (SpA-RHPA). Hemolytic plaques were most distinct and numerous when peripheral blood mononuclear cells were stimulated with 6.9 micrograms/ml pokeweed mitogen for 7 days. Immunoglobulin-secreting cells were identified morphologically within a zone of hemolysis utilizing a 1:5 dilution of rabbit anti-cat IgG and a 1:30 dilution of guinea pig complement as developing reagents. The SpA-RHPA system should contribute to an understanding of normal feline T- and B-lymphocyte interactions and will likely aid in the identification and understanding of immune cell dysfunctions associated with chronic feline leukemia virus infection.

Plaque-forming cells in man. IV. Influence of acetylsalicylic acid in vivo and dexamethasone in vitro

The influence of acetylsalicylic acid (ASA) and steroid (ST) on the number of plaque-forming cells (PFC) developed in pokeweed mitogen-activated cultures of peripheral blood lymphocytes (PBL) was investigated. Cultures of 10(6) PBL were established from blood samples of 16 healthy volunteers before and after intake of 2 g of ASA, and parallel cultures were supplemented with ST in vitro. The immunoglobulin secretion was monitored with a protein A assay. Our results show that pharmacological doses of ASA in vivo decrease the number of PFC by 41%, whereas the distribution of the subpopulations was unaltered. In cultures of PBL obtained before the intake of ASA and supplemented with 10, 50 or 100 micrograms/ml of dexamethasone the number of PFC was decreased by 50%, 41% and 44%, respectively. In cultures of PBL obtained after the intake of ASA and supplemented with 10, 50 or 100 micrograms of ST, the number of PFC was further decreased by 22%, 32% and 38%. The effects of ASA in vivo and ST in vitro were additive. The ratio of IgM, IgG and IgA PFC was unaffected by ASA and ST. It is suggested that the modulation of the PFC response induced by ASA and ST is mediated by the prostaglandin system.