Naturally occurring, spleen-associated suppressor activity of the newborn mouse. Biochemical and functional identification of three monokines secreted by newborn suppressor-inducer monocytes

Immature monocytes residing in the spleens of newborn mice less than 6-7 days of age are known to suppress T-dependent and T-independent immune responses in vitro and in vivo. Suppression is mediated in part through products secreted by the newborn monocytes. In the present study, we have identified 3 monokines secreted by newborn, but not adult, monocytes correlating with materials possessing significant suppressor activity in vitro. These monokines have molecular weights of 58, 10.8, and 10 kilodaltons, appear to be proteins, and are insensitive to heat inactivation. The 58 kd material is antigenically distinct from alpha-fetoprotein, while the lower molecular weight materials are too large to be prostaglandins. Although these monokines can be shown to have activity in vitro, they are not as efficient as newborn monocytes in preventing alloreactivity in vivo.

Human cord blood suppressor T lymphocytes: I. Phenotype and target of the inducer of suppressor cell factor

The present study examines the characteristics of the cord suppressor T cells and their targets. When an inducer of suppressor T cell factor (TisF) from culture supernatant of alloantigen-activated cord lymphocytes was used as a source of suppression, adult lymphocyte response to soluble antigen candidin, alloantigens, and pokeweed mitogen were all suppressed. These results suggest that TisF acts primarily on T cells in an antigen-nonspecific fashion. Furthermore, preculture T cell irradiation, but not T8+ cell depletion, of adult lymphocytes abrogated the suppressive effect of TisF on the PWM-stimulated IgG production, suggesting that the target of TisF belongs to the radiosensitive T8-(T4+) T cell subset. When different cord T cell subsets were tested for suppressor activity, only radiosensitive T4+ cells were capable of suppressing IgG production by adult lymphocytes. Neither preculture T8+ cell depletion nor irradiation of adult T cells affected the suppression. Taken together, these results suggest that the suppressor activity of cord T cells originated from an inducer of suppressor cells that activates radiosensitive T4+ suppressor effector cells through TisF. In turn, these effector cells act on either radioresistant T4+ helper T cells or B cells or both.

Purification and analysis of isoforms of soluble immune response suppressor (SIRS)

Soluble immune response suppressor (SIRS) isolated from the T cell hybrid 393D2.6 was originally reported to exist as at least two m.w. forms and to migrate on reverse-phase high-performance liquid chromatography columns as three separate species. In experiments presented here, a further analysis of the different chromatographic forms of SIRS has been carried out. SIRS-alpha elutes from C-18 reverse-phase columns in 20% propanol. When SIRS-alpha is subjected to isoelectric focusing, three biologically active species are isolated at approximately pH7, approximately pH6, and approximately pH5 (SIRS-alpha 7, SIRS-alpha 6, and SIRS-alpha 5, respectively). SIRS-beta elutes in 30% propanol, and on isoelectric focusing the biologic activity is found only at approximately pH7 (SIRS-beta 7). Both the alpha and beta forms of SIRS have nearly identical m.w. when subjected to molecular sieve chromatography and migrate with a m.w. of 11,000. The molecular basis for these isoforms is not yet clear but is consistent with earlier studies showing two separate messenger RNA species coding for SIRS.

Effect of Bacillus Calmette-Guérin on the in vitro generation of cytotoxic T lymphocytes. II. Role of interleukin-1-like factors and of soluble suppressor factors

The injection of BCG vaccine in C57BL/6J mice results in the suppression of the generation of cytotoxic T lymphocytes (CTL) in mixed lymphocyte cultures (MLC) and of mitogenic reactions to concanavalin A (Con A). Suppression is mediated by macrophage-like suppressor cells. Since previous work had indicated that suppression involved the inhibition of the production of interleukin-2 (IL-2), the effects of BCG on interleukin-1 (IL-1), a monokine required for IL-2 production, were investigated. It was found that the release of IL-1-like activity in spleen cell cultures stimulated with LPS or Con A was increased by previous BCG treatment of the cell donors. In MLC, the release of IL-1-like activity was also increased by BCG. However, the detection of IL-1-like activity in MLC supernatants was prevented by the presence of a suppressor factor. In this case, the IL-1-like activity could be separated with gel filtration from the suppressor factor which had higher molecular weight. The production of IL-1-like activity by CBA/J spleen cells, which are not suppressed by BCG, was not significantly different from that of C57BL/6J cells, which are markedly suppressed. Moreover, the addition of IL-1 to the BCG-suppressed cultures not only did not restore normal reactivity, but actually further suppressed CTL formation. It was concluded that BCG-induced suppression cannot be attributed to decreased IL-1 activity. The suppressor factor discovered during these investigations may have a role in this type of suppression.

[Plaque-forming cell (PFC) technique in the assay of serum blocking activity in lung cancer]

The serum blocking activity of 32 patients with lung cancer was assayed by means of PFC technique and half-hemolysis concentration (HC50) test. The results showed that the serum from lung cancer patients had an obvious immunosuppressive effect on antibody production of C3H mice. The PFC number of mice which had received an injection of serum from lung cancer patient was significantly lower than that of the control group which was given an injection of 0.9% saline solution (47.3 +/- 2.9, 89.8 +/- 6.9, P less than 0.01). The serum from patients with various benign lung diseases and healthy adults did not show such immunosuppressive effect (86.5 +/- 8.6, 75.7 +/- 6.0). The results examined by HC50 test also indicated that the antibody level of mice injected with the serum from lung cancer patients was obviously lower than that of control mice (56.3 +/- 3.0, 82.09 +/- 5.0, P less than 0.01). The immunosuppression incidence of serum from lung cancer patients (16/32) was significantly higher than that of serum from patients with benign diseases (3/19) or from healthy adults (2/18). The positive rate of the serum blocking activity in lung cancer patients was 50% which was significantly higher than that of the other two groups. There was no correlation between the immunosuppressive activity and stage or histologic classification of lung cancer. It was also found that higher incidence of immunosuppressive activity was present in the early lung cancer. The result suggests that the serum immunosuppression test using PFC technique be valuable in the early diagnosis of lung cancer.