Suppressor cells generated from human peripheral mononuclear cells by stimulation with pokeweed mitogen

Spontaneous thyroglobulin autoantibody production by peripheral blood lymphocytes is regulated by T cells and is augmented by soluble T cell factors

In this study we report the spontaneous production of autoimmune anti-thyroglobulin antibodies (Tg Ab) by peripheral blood lymphocytes from patients with autoimmune thyroid disease and the use of these cells to study the regulation of this production in vitro. Using a mitogen free microculture system we have found a significant correlation between an individuals' serum titre and the amount of Tg Ab produced in vitro. At low B:T cell ratios Tg Ab production decreased. Specific depletion of suppressor T cells and helper T cells was accomplished using the monoclonal antibodies OKT 8 and OKT 4 respectively. Suppressor cell depletions resulted in increases in Tg Ab production while depletion of helper cells had no consistent effect. The addition of pokeweed mitogen had no stimulatory effect on spontaneous thyroglobulin antibody production. In contrast, when T cell conditioned media was added to the cells, Tg Ab production increased substantially in all patient cultures tested but not in normal control cultures. The results of this study are consistent with the existence of functional thyroid-antigen specific suppressor cells in the peripheral blood which are actively involved in the regulation of autoantibody producing B cells. The results obtained with the cultures maintained in conditioned media show that autoimmune lymphocytes are extremely sensitive to one or more stimulatory factors present in the media and suggests an important role for the production of soluble lymphocyte factors and the expression of receptors for these factors in the aetiology of autoimmune thyroid disease.

The influence of autologous cell interactions on spontaneous and pokeweed mitogen-induced immunoglobulin production

Both helper- and suppressor-T-cell activities are generated in the autologous mixed lymphocyte reaction and in pokeweed mitogen (PWM)-stimulated cultures. The addition of low numbers of irradiated non-T cells enhance while high numbers suppress spontaneous and PWM-stimulated IgG synthesis by autologous cells. Monocytes are the principal inducers of suppression and exert their influence within the first 24 hr of culture. Suppression in association with PWM stimulation is nonspecific in nature, T-cell mediated, partially radiosensitive, and resistant to hydrocortisone. Neither indomethacin nor dibutyryl cyclic AMP reverses monocyte-related suppression. These findings suggest that the outcome of in vitro Ig synthesis assays is critically dependent upon monocyte-T-cell interaction.

Increased IgA-producing cells in the blood of patients with active Henoch-Schönlein purpura

Peripheral blood lymphocytes (PBL) producing IgA, IgM, and IgG, both spontaneously and after pokeweed mitogen stimulation in cell culture, were determined by a protein A hemolytic plaque assay in 20 children with active Henoch-Schönlein purpura (HSP), 42 with inactive disease, 22 normal controls of the same ages, and 18 children with upper respiratory tract infections (URTI). The geometric mean of circulating IgA-producing cells in active HSP (1,016 X divided by 1.55 cells/10(6) PBL) was increased when compared with the group with inactive disease (P less than 0.001), normal controls (P less than 0.001), and children with URTI (542 X divided by 2.03 cells/10(6) PBL, P less than 0.05). The number of circulating IgM-producing cells was slightly increased in active HSP (260 X divided by 2.65 cells/10(6) PBL) and URTI (256 X divided by 3.16 cells/10(6) PBL). Both values were higher than those found in the group with inactive disease (113 X divided by 2.26 cells/10(6) PBL, P less than 0.01). There were no significant differences among the 4 groups in the number of circulating IgG-producing cells. The number of cells producing each type of immunoglobulin after in vitro stimulation with pokeweed mitogen was similar in patients with active HSP, normal controls, and the group with inactive disease. These data demonstrate a selective increase in the number of circulating IgA-producing cells only during disease activity, and add further support to a possible pathogenic role of this immunoglobulin in HSP.

Induction of monocytic suppression after stimulation of peripheral human mononuclear cells with staphylococcal protein A and Staphylococcus aureus

Staphylococcal protein-A (SPA) and Staphylococcus aureus are known to be polyclonal human B-cell activators. It was noted that they induced plaque-forming-cell (PFC) responses lower than those induced by pokeweed mitogen (PWM) and the possibility of early triggering of a suppressor cell was investigated in the present series of experiments. Peripheral mononuclear cells (MNC) were passed through Sephadex G-10 columns to eliminate monocytes. The PFC responses to SPA and S. aureus were thereby increased. PWM-driven PFC responses are suppressed by the simultaneous presence of SPA in a dose-related way, if present in the early phases of the cultures. MNC precultured with SPA or S. aureus have the ability to suppress the PFC response of autologous MNC to PWM. Interestingly this suppressor cell activity was radiation resistant and could not be abrogated by treatment with anti-T-cell monoclonal antibody plus complement. The above experiments clearly demonstrate that the observed low PFC responses of MNC after stimulation with SPA and S. aureus are due to the induction of suppressor cells by these stimulants. The suppressor cells are apparently of monocytic origin.

Inhibition of human antigen-induced lymphoblastoid B-cell function by an in vivo-induced suppressor T cell

Lymphoblastoid (LB) B cells which spontaneously produce antitetanus toxoid IgG antibodies (Tet-IgG) in short-term cultures (3 days) appear in the circulation 5-7 days after immunization with tetanus toxoid. Addition of pokeweed mitogen (PWM), normally a stimulator of antibody production, caused instead a reduction in the in vitro synthesis of Tet-IgG by the LB cells. In order for this inhibition of antibody production to occur, T cells had to be present, and the inhibition was proportional to the number of T cells added to the culture, demonstrating the existence of PWM-inducible suppressor cells. The cells mediating the suppression had the OKT8 phenotype and also exhibited the following characteristics: (1) a PWM pretreatment period as little as 14 hr was enough to complete activation; (2) conventional inhibitors of suppressor T cells as hydrocortisone and cyclosporin A only partially reversed its effect; and (3) DNA synthesis was not required. The T-suppressor activity was detectable in the circulation before immunization, increased two- to fourfold by 5-12 days after boosting, and waned after 3 weeks. The mechanism of action of this suppression does not appear to involve conventional cytotoxic T cells as (1) the suppression was mediated across allogeneic barriers and (2) the suppression could not be reversed by inclusion of anti-Leu-2a antibodies in the culture. These results suggest that this suppressor T-cell subset may be important in the normal regulation of activated stages of human B lymphocytes.