The production of mouse peroxidase:antiperoxidase (PAP) complexes suitable for immunohistological use in conjunction with monoclonal antibodies is described. Three approaches were explored: 1) production of conventional polyclonal PAP complexes; 2) conversion of rabbit PAP to "pseudo-mouse PAP" by incubation with monoclonal mouse anti-rabbit immunoglobulin; 3) formation of PAP complexes from monoclonal mouse antiperoxidase. PAP complexes prepared by the latter technique gave the best PAP LABELING OF MONOCLONAL ANTIBODIES

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A chronic suppression of Igh-1b and Igh-3b (IgG2a and IgG2b of b haplotype) allotype expression has been induced by injecting T splenocytes from normal BALB/c or BC8 mice into newborn F1 hybrids of appropriate Igh congenic strains: BALB/c into (BALB/c Igha X CB20 Ighb)F1 and BC8 into (BC8 Igha X C57BL/6 Ighb)F1 or (C57BL/6 X BC8)F1. This suppression does not affect IgM (IgH-6b) or IgA (Igh-2b) expression. When the Ighb haplotype is paternally transmitted, the proportion of T splenocyte recipients showing allotypic suppression increases with time reaching 70% 40 weeks after birth. We also succeeded in inducing this pattern of suppression in 2 out of 13 cases when the Ighb was inherited from the mother. These normal T splenocytes are therefore clearly allotype specific. As Igh-6b production is not affected by the suppression, these T splenocytes are believed to influence B cells more or less committed to Igh-1b or Igh-3b production rather than more precocious Igh-6b (IgM of b haplotype) carrying precursors in the classical IgM-IgG filiation pathway.

Lipopolysaccharide extracted from Bordetella pertussis was mitogenic for spleen cells of endotoxin-resistant C3H/HeJ mice. Although endotoxic lipid A was inactive, mitogenic activity of lipopolysaccharide was exhibited by purified preparations of polysaccharides I and II, which constitute the carbohydrate moiety of the macromolecule. These low-molecular-weight (2,800 and 3,600) polysaccharides, containing carboxyl groups, were not mitogenic for thymocytes and splenic T-cells of C3H/HeJ mice, but did show mitogenic activity for splenic B-cells of C3H/HeJ mice and for spleen cells of C57BL/6 athymic nude mice. The mitogenic activities of polysaccharides I and II were also compared with those of other polyanionic polysaccharides, and the results indicate that high molecular weight is not necessary, and negative charges are not sufficient, for mitogenicity.

T cell-induced IgG2ab allotype suppression provides a physiological model for the study of T cell responsiveness or tolerance to this Ig allotype. Normal, untreated mice of the Igha haplotype possess a basic and easily amplifiable T cell reactivity against the expression of IgG2ab, while their Ighb congenic mice produce substantial levels of this Ig and thereby are tolerant to this self-protein antigen. Therefore, the involved TCR repertoire in Igha and Ighb congenic mice is different. We have previously shown, in Ighb and Igha/b mice perinatally deprived of IgG2ab expression, that T lymphocytes bearing anti-IgG2ab TCR can emerge and induce an autoimmune suppression of IgG2ab. Correlatively, full and IgG2ab-specific T cell tolerance can be induced in Igha mice by their perinatal exposure to this Ig allotype. In this physiological model, which involves neither superantigens nor TCR-transgenic T cells, the responsive or tolerant state in Igha mice is assessed in vivo by the capacity to induce or not a T CD8(+)-dependent suppression of IgG2ab allotype production in Igha/b recipients of these cells. Taking advantage of this system, we were able to demonstrate here that, over the long term, this perinatally induced, IgG2ab-specific T cell tolerance was not definitively acquired, and that a spontaneous and total tolerance breakdown was observed by the age of 6 months. Furthermore, we showed that perinatal followed by prolonged tolerogen treatments up to 3, 6 and even 9 months of age were no longer sufficient to assure definitive T cell tolerance acquisition to IgG2ab, as the T cell suppression-induction capacity of Igha mice was partially and then entirely restored 3-6 months after the end of the tolerogen administration.