In vitro proliferation of murine spleen cells: genetic control of proliferative responses induced by phorbol ester and calcium ionophore A23187

Retrovirus-induced lymphoproliferative disease in mice undergoing graft-versus-host reaction

The effect of graft-versus-host reaction on the course of concommitant retrovirus-induced lymphoproliferative disease was investigated. The graft-versus-host reaction was elicited by a single i.v. injection of 1.2 x 10(8) parental spleen cells into adult F1 mice. Lymphoproliferative disease was induced by a single transfusion of 0.2 ml of whole blood from donors with fully developed disease, induced by infection with retrovirus LP-BM5 MuLV. Graft-versus-host reaction and the lymphoproliferative disease each separately produced similar syndrome consisting of splenomegaly, lymphadenopathy, leukopenia, neutrophilia, reduced in vitro proliferation of spleen cells and suppression of in vivo immune responsiveness. The above symptoms were usually less pronounced during graft-versus-host reaction. Ongoing graft-versus-host reaction neither aggravated nor accelerated the course of the virus-induced lymphoproliferative disease in genetically susceptible F1 hybrids. Likewise, an ongoing graft-versus-host reaction in genetically resistant F1 hybrids did not alter their susceptibility to the retrovirus infection. The apparent lack of the effect of graft-versus-host reaction -dependent immunosuppression on the severity and the course of the concommitant retrovirus-induced lymphoproliferative disease suggests pathogenic differences between the murine syndrome and human AIDS for which the murine disease is considered by some to be an animal model.

Retrovirus-induced lymphoproliferative disease in mice: role of humoral immunity in perinatally exposed mice

The mice born to female mice infected with LP-BM5 MuLV, the etiologic agent for lymphoproliferative disease and nursed for 4-6 weeks by them were less susceptible upon reinfection by i.v. transfusion of blood or plasma from infected donors with fully developed disease. Sera of 7 week or older perinatally exposed mice were capable of a complete in vitro neutralization of virus in plasma or blood from mice with fully developed disease. In contrast, sera from 3-week old perinatally exposed mice were ineffective. The neutralizing ability of the sera was drastically reduced or abrogated after their absorption with anti-mouse IgM. These observations are consistent with the notion that perinatally exposure results ina moderate form of the disease of the offspring. This perinatal infection is followed by a production of neutralizing antibodies of predominantly the IgM class that significantly alters the course of the lymphoproliferative disease and, in some instances, even prevents its development.

Acquired immunodeficiency in murine lymphoproliferative disease: considerations on pathogenesis

C57BL/6Kh mice were infected with a single i.p. injection of 1 x 10(5) FFU of LP-BM5 MuLV. The development and progress of the virus-induced lymphoproliferative disease was followed for 12 weeks after infection. As anticipated, progressive splenomegaly and lymphadenopathy, as well as almost total abrogation of immune responsiveness ensued. In contrast to previous reports, there was a dramatic increase in the frequency of CD4+ cells in spleens among which over 20% expressed V beta 5 TCR, as compared with fewer than 3% in spleens of normal mice. Spleen cells from infected mice retained their in vitro ability to proliferate upon stimulation with IL-2 and anti-CD3, but were unable to respond when stimulated with phorbol ester and either a low dose of IL-2 or calcium ionophore (ionomycin). A similar pattern of in vitro proliferative responses was obtained when normal spleen cells were treated with K252a compound, a known inhibitor of protein kinase C activity. Together with the observations that viral infection impaired down-regulation of the phorbol-induced kinase activity and that the kinase inhibitor only marginally enhanced suppression of virus-infected cells proliferation, this finding suggests that disturbances of protein kinase C activity may underly the pathological effects seen after viral infection. However, since no apparent quantitative and qualitative changes in protein kinase C itself and its translocation were observed, it is more likely that the virus may interfere with either the substrate or product of kinase activity.

Murine AIDS: a model for the human disease or a distinct entity?

The LP-BM5 mixture of murine retroviruses elicits a disease in mice referred to as murine immunodeficiency syndrome (MAIDS) that is considered by some to be an animal homologue of human AIDS. In this article, we present and discuss some recent findings on the pathogenesis of the murine disease and their implications for the proposed homology between murine and human syndromes. The murine disease seems to display as many similarities to as it does differences from human AIDS. Among the latter are: definitive and exclusive viral etiology, a strong genetic effect on susceptibility to infection, expansion of the CD4+ cell population in spleen and peripheral blood, consistent transmissibility by a single transfusion of the minute amounts of blood or plasma from infected donors, and striking similarity between virus-induced alteration of the in vitro spleen cell proliferation and those caused by treatment with a protein kinase inhibitor K252a. With this in mind, the use of the noncommittal term retrovirus-induced murine lymphoproliferative disease instead of MAIDS appears to be more appropriate at this time.

Postnatal development of murine spleen cell proliferative responses induced by interleukin 2 or phorbol ester and calcium ionophore A23187

To determine the kinetics of the ontogeny of polygenically controlled proliferative responses, spleen cells from 5, 10 and 20 day-old mice, previously identified as high (B10.PL-Thy-1a, AKR.M) and low (C3H.A) responders were tested. Cells (10(5)) were simulated in vitro with human recombinant IL-2 (35 U), a mixture of either IL-2 (0.7 U) and 13-myristate 12-acetate phorbol (5 ng) or phorbol and calcium ionophore A23187 (5 ng). Two parameters were assessed; proliferation measured by 3H-thymidine incorporation and the synergistic effect expressed as a synergism coefficient (SC): the ratio of proliferation induced by a mixture to the sum of proliferations induced by each component alone. At the age of 5 days, all three strains, regardless of stimulation, produced similar proliferation and showed no synergistic effect (SC = 1.0). At the age of 10 days, proliferation of high responder cells was 3-5 times higher than that of the low responder, but only high responders displayed marginal synergistic effect (2 greater than SC greater than 1.5). At the age of 20 days, proliferative responses of the high responders increased somewhat and a definitive synergistic effect became clearly demonstrable (SC greater than 3.0). This effect increased further after the age of 20 days to reach the level of SC greater than 5.0 in adult high responders. The delay in expression of synergistic effect was due to a substantial proliferation induced by phorbol alone in 10 day-old animals. The available data allow the conclusion that phenotypic strain variation in proliferative responses is first detectable at the age of 10 days and becomes fully developed only after attaining the age of 20 days or more. Since the magnitude of proliferative responses was not associated with frequencies of IL-2R alpha + cells it seems that differences in responsiveness can not be attributed to the induction of IL-2R alpha chain, and they may reflect intrinsic abilities of cells to proliferate.

Cell-surface molecules in the regulation of immune responsiveness

This paper reviews current knowledge genetics, structure and function on three categories of cell-surface molecules that affect immune responsiveness. It is focused on human molecules, but some references to murine analogues are made. First, the Major Histocompatibility Complex (MHC) molecules are discussed from the point of view of the associative recognition of antigenic peptides. The multiplicity, polymorphism and heterozygosity of MHC genes is correlated with the fine structure and the function of the molecules encoded by these genes. Second, selected CD molecules that are involved in cell-cell interaction and transduction of signals are discussed and correlated with discrete subsets of T cells, finally, some cell-surface receptors, antigen-specific and interleukin-specific, are analyzes, the effect of various molecules on immune responsiveness is illustrated by the actual experimental data. A minimal or parsimonious of triggering an immune response in which the discussed molecules are involved is described as a starting point for further discussion.