Jitka Chutná

Antigen-mediated macrophage adherence inhibition

Abstract Antigen-mediated macrophage adherence inhibition (MAI) was studied in inbred rats immunized with various transplantation, tumour-specific and protein antigens. A macrophage-rich suspension of peritoneal cells (PC) was obtained from the peritoneal cavity of immunized and control animals by washing. The adherence to glass of PC was specifically inhibited by the addition of the antigens used for sensitization of PC donors or by related (cross-reacting) antigens but not with unrelated antigens. The MAI seems to be due to the direct interaction of the respective antigen with a corresponding PC receptor and not due to the humoral factor released from immune lymphocytes of PC population upon contact with the specific antigen.

Immunological tolerance and tumour allografts in the brain

THE brain has been considered to be an immunologically privileged site with regard to tissue transplantation. In addition, a loss of ‘tumour surveillance’ due to a weakening of the immune system in the brain has been postulated. The data on the brain as a privileged site are not unequivocal, however. The evidence for and against this thesis has been discussed by Woodruff1 and Lance2. Barker and Billingham3 also speculated that “reports that the brain can prevent implanted homografts from inciting sensitivity because it lacks a lymphatic drainage, thus having no afferent pathway of the immunological reflex, are more equivocal”. The need for a critical re-evaluation of the brain as a privileged site has been stressed. We report here a study of the possible action of immunological tolerance in the brain and of the sensitivity of normal rats and tolerant rats to inoculation of allogeneic tumour cells into the brain. We show that transplantation tolerance is involved even in the brain; thus demonstrating the presence of specific immunity following inoculation of tumour cells into the brain. This finding suggests that previously held views of the brain as a privileged site may not be entirely valid and that specific immune processes are accomplished in the central nervous system.

Participation ofH-2 regions in neonatally induced transplantation tolerance

At least three strong histocompatibility (H) loci--the H-2K, H-2D, and H-21 (for review see Klein 1975)--have been demonstrated within the H-2 complex of the mouse, and additional subregions have been defined within the 14-21 region (Shreffler and David 1975). The products of individual loci differ in their physicochemical properties (Hess 1976), immunogenicity (McKenzie and Snell 1973, McKenzie and Henning 1976), and ability to induce enhancing antibody formation (McKenzie and Snell 1973, Staines et al. 1974, Davies and Staines 1976, McKenzie and Henning 1977a, b). The ease with which transplantation tolerance can be induced is related to the genetic disparity between the donor-recipient strain combinations (for review see Silvers and Billingham 1969). Which of the H-2 products might be a major obstacle to overcoming the tissue incompatibility is still unexplained, however. Antigens which stimulate in mixed lymphocyte culture (MLC) have recently been thought to provide the major barrier to tolerance induction in H-2-incompatible combinations (Brent et aL 1976, Brooks 1976). We have tested neonatal tolerance induction in six combinations of H-2-congenic strains in such a way as to provide differences in the entire H-2 complex or in only a small proportion of it. The results presented here indicate that tolerance induction is much more difficult when donor and recipient differ at the K region than when they differ at the D and/or 1regions. All mice were from inbred strains maintained at the Institute of Molecular Genetics, Czechoslovak Academy of Sciences, Prague. The following inbred strains, congenic resistant partner strains, and F 1 hybrid mice were employed: B10.A, C57BL/10ScSn (hereinafter abbreviated B10), B10.D2, B10.AQR, B10.A(2R), B10.A(4R), A.TL, A.TH, (B10.A x B10)F~, (B10.A • B10.D2)F1, (B10.A • B10.AQR)F~, [B10.A x B10.A(2R)]F~, [BI0.A • B10.A(4R)]F1, and (A.TL • A.TH)F r The H-2 genotypes of these strains are listed in Table 1. Tolerance was induced in newborn mice (up to 20 hours of age) by the intravenous injection of 1215 • 10 6 living hybrid spleen cells. Cell suspensions were prepared in Hanks buffered solution from spleens of 2-3-month old donors and injected in a volume of 0.07-0.09 ml into the orbital branch of the anterior facial vein. At 8-9 weeks, the neonatally treated recipients were grafted with the respective allogeneic tail skin, according to standard procedure (Billingham et al. 1954). Grafts were inspected daily the first 4 weeks after transplantation and twice a week thereafter. The success of tolerance induction depended on H-2 antigenic difference between donor and recipient.

Induction of transplantation tolerance using serum as antigen source

IT has been shown that massive doses of allogeneic serum produce the prolongation of renal allograft survival in adult pigs1. Furthermore, alloantigenic activity was demonstrated in human serum by inhibiting certain reactions in vitro2–6; and in some strains of mice, the presence of histocompatibility (H) antigens in the serum could be demonstrated by inhibition of the cytotoxicity of specific alloantisera7.

The regulatory role of I-J subregion in neonatal tolerance induction to H-2D alloantigens.

The mechanism of neonatally induced transplantation tolerance was studied in two mouse strain combinations involving differences at the D region of the H‐2 complex only or at the same D region plus I‐J subregion (including I‐E, I‐C, S and G regions). In the strain combination with the H‐2D difference only, cells from tolerant mice proliferated markedly in the MLR assay when incubated with antigens tolerated in vivo, whereas the MLR reactions were negative in the combination with D plus I‐J region disparities. In the latter combination cells from tolerant mice also did not respond to third‐party antigens and their incubation with the tolerated antigens led to the suppression of cell proliferation. This non‐specific suppression was absent in cells from tolerant mice in the strain combination, which differed in I‐C, S, G and D alloantigens. Specific suppressor cells, which inhibited the development of cytotoxic cells, were demonstrated in tolerant mice of both strain combinations. The results show that, in addition to the specific suppressor cells induced by H‐2K or H‐2D alloantigens, non‐specific suppressor cells induced by the I‐J region disparity that may regulate the resultant activity against H‐2D (and probably also H‐2K) alloantigens are involved in transplantation tolerance.

Attempts to compare the effectiveness of blocking factors and enhancing antibodies in vivo and in vitro.

Sera from rats carrying tolerated skin allografts were tested for the presence of blocking activity in vitro. Sera with blocking activity had no effect on transplantation tolerance induction in newborn animals. Immunological enhancement of tumor growth was procured by passive transfer of serum from tolerant animals bearing skin allografts. It made no difference whether or not the serum contained blocking activity in vitro. These results suggest that there is no relationship between blocking factors and enhancing activity in vivo.

Heterogeneity of tolerance to xenogeneic cells in mice inoculated at birth with rat cells

Abstract In experiments on induction of tolerance to xenogeneic cells in newborn mice with rat bone marrow cells, higher mortality was not observed even after repeated injection of cells, hence no graft-versus-host disease (GVHD) occurred. Xenogeneic skin grafts were not tolerated and showed little significant prolongation of survival. Nevertheless, complete suppression of cytotoxic antibody formation was detectable in most of the treated animals in which no graft survived longer than 12 days. At the cellular level, complete tolerance in MLC and cytotoxicity assays was also observed in the majority of animals. Thus, different detection systems seem to be a decisive criterion in detecting the tolerance state and the individual specific mechanisms of immunity may be dissociated in the split tolerance studied in the xenogeneic system in the present experiments.

Comparison of the sensitivity of in vivo detection of immunological tolerance in the xenogeneic system.

Abstract Three systems for the detection of xenogeneic tolerance in vivo are compared; skin xenografts, implantation of a tumour xenograft subcutaneously, and implantation of a tumour xenograft into the brain. Implantation of tumour tissues into the brain has appeared to be the most sensitive test of immunological tolerance owing to the anatomical and immunological peculiarities of the brain.

Passive immunological enhancement of muscle allografts in rats.

The effect of the passive administration of antiserum obtained from recipients immunized with antigens from H-1 + non-H-1 incompatible donors on muscle allograft survival in rats was studied. In transplantation across the non-H-1 antigenic barrier (H-1 compatible but non-H-1 incompatible) a satisfactory degree of immunological enhancement was achieved. Recovery of contractile properties of muscle allografts after different immunological treatments of the recipients was compared.