Response of tumour-related and normal lymphocytes to antigens on fibroblasts from embryos of varying age

Pregnancy induced mammary tumor specific effector cells are present long after parturition in a breast cancer model in rats

Pregnancy is known to provide protection against 7,12 dimethylbenz[a]anthracene-(DMBA) induced mammary carcinogenesis in rats. We observed in earlier studies that splenocytes of parous rats have significant cytotoxicity against mammary tumor cells both in vitro and in vivo. However, it remains to be established how long these cytolytic cells persist after parturition in parous host. The present study was designed using parous rats, 36 or more days after parturition. We observed that fresh splenocytes from these rats had low cytolytic activity against mammary tumor cells. However, when these cells were re-stimulated with irradiated mammary tumor cells in vitro, they had significantly higher cytotoxicity against mammary tumor cells. These studies show for the first time that pregnancy induced cytotoxic splenocytes are present long after parturition and they can be restimulated in vitro to enhance the cytotoxic effect.

Maternal immune responses to oncofetal antigens

The maternal host responds immunologically to antigens of the fetus. While the immune responses to paternally derived alloantigens and to placental antigens have been intensively studied, the immune responses to oncofetal antigens have been relatively unexplored. Oncofetal antigens are present on fetal and malignant tissues but absent from normal adult somatic tissues. These antigens elicit both cell-mediated and humoral immune responses in the parous female. Limited data suggest that these immune responses may influence reproductive processes. More investigation in this area is desirable.

In vitro analysis of immune responses of inbred guinea pigs infected in vivo with Leishmania enriettii and an investigation of active immunization of susceptible animals

Adherent skin cell monolayers have been prepared from the infected area of inbred guinea pigs inoculated with Leishmania enriettii. Cells from those animals most susceptible to disease (2/N) are less able to promote proliferation and the production of macrophage migration inhibition factor (MIF) from leishmania-immune lymphocytes than are infected cells taken from the more resistant 13/N or (2/N X 13/N)F1 animals. Exposure of immune lymphocytes of all strains to parasite antigen in the relative absence of autologous antigen-presenting cells induced the development of a suppressor pool capable of inhibiting lymphocyte proliferation in response to immunogenic signals. Decreased lymphocyte proliferation during the course of disease may be caused by the endogenous release of products of arachidonic acid metabolism from host monocytes, though along with the decline in DTH reactivity in infected animals, and apparently in concert with the healing of the primary lesion, there occurs an increase in titer of anti-leishmania antibody in infected animals. Preliminary attempts to confer protection of naive animals by preimmunization with lymphocytes from previously infected, susceptible, or resistant guinea pigs suggested a role for interacting "helper" and suppressor lymphocyte pools in the immunoprotection from leishmania infection.

Reaction of the leukocytes of melanoma patients and control donors, including pregnant women, with melanoma- and fetus-derived materials

Using a one-stage capillary leukocyte migration inhibition assay, we examined peripheral blood leukocytes from 97 patients with malignant melanoma, 194 pregnant women, and 123 non-pregnant donors for their reactivity with materials from fetal and melanomatous tissues. As in previous studies, we found melanoma extracts selectively to inhibit melanoma patients' leukocytes. First-trimester fetal extracts also selectively inhibited melanoma patients' leukocytes, suggesting their cross-reactivity with melanoma-derived antigens. We could not localize the source of the inhibitory materials within the fetuses. We found no evidence that pregnant women were selectively immunized to fetal or melanoma extracts, regardless of their parity or the stage of their pregnancy.

Tumour-cell susceptibility to cytotoxic or cytostatic effector cells in vitro and the regulation of tumour-cell growth in vivo

Tumour-cell growth in lung nodules after i.v. transfer to sublethally irradiated mice has been followed after adoptive transfer of different populations of lymphoid cells. Spleen cells deliberately immunized in vitro and in vivo against stimulator cells bearing embryo-associated antigens and which are cytostatic in vitro for targets bearing such antigens, can diminish the number of lung nodules found after i.v. transfer. In contrast, cytotoxic (in vitro) spleen cells, while capable of diminishing local (s.c.) growth of tumour cells, cannot control systemic tumour growth. Within a given solid tumour mass, the subpopulations resistant to cytostatic effector cells in vitro are the ones most likely to produce lung colonies after adoptive transfer in vivo, though they show no more local (s.c.) growth than to cytostatic-sensitive cells in vivo.

Inhibition of cell proliferation rather than of cell lysis as a measure of immune reactivity in embryo-antigen-challenged mice

An assay system is described in which effector cells added along with suitable target cells inhibit, in a quantitative fashion, the subsequent uptake of 3H-thymidine by those target cells. Effector cells active in this assay, using embryonic fibroblast cells as targets, develop spontaneously in cultures of mouse lymphoid cells, but are apparently different from those described earlier by investigators of activity in cytotoxic assays. Further evidence is presented to show the development of spleen-derived effector cells with cytostatic activity (for embryonic fibroblast target cells) in mice during the course of normal pregnancy, or growth of spontaneously appearing mammary adenocarcinomas. Indeed, such effector cells can also be found within the growing solid mass itself. Different populations of tumour cells isolated from a solid tumour apparently differ in their susceptibility to growth inhibition by tumour-bearer-derived cytostatic effector cells, a phenomenon which may be related to metastatic spread of tumour cells.

Organ-related and malignancy-associated reactivity of cancer patients' leucocytes: a leucocyte migration study with tumour and foetal extracts

Leucocytes from patients with a variety of tumours including gastric, colorectal, lung, kidney and mammary cancer, were tested in the leucocyte migration test (LMT) against organ-related and non-organ-related tumour and foetal extracts. The reactivity of cancer patients' leucocytes against a panel of organ-related tumour extracts was found to be 71-93%, depending on the tumour system tested. Cross-reactivity with a panel on non-organ-related tumour extracts was found in 0-38% of patients. Corresponding patterns of reactivity were obtained by testing patients' leucocytes against human foetal organ extracts; pathological migration indices (MI) were found in 70% of tests in which patients' leucocytes were reacted with organ-related extracts, and in 16% of tests with non-organ-related extracts. The data strongly support the concept that patients' leucocytes are sensitized to cross-reactive foetal determinants of organ-related specificities. Furthermore, it is proposed that foetal extracts as inducers of lymphokine production in presensitized lymphocytes could be used efficiently and reproducibly as a source of foetal antigen, as well as in the clinical application of the LMT procedure.