In vivo isotype regulation of humoral responses to dextran B1355 in BALB/c mice. Double-class IgG3/IgM producers as a function of age.

This report shows that, in 8- to 10-month-old BALB/c mice immunized intraperitoneally with dextran B1355, approximately 75% of IgG3 anti-alpha (1----3) polyglucan (anti-dex) plaque-forming cells (PFC) detected in the spleen were identified as double-Ig class producers secreting simultaneously IgG3 and IgM antibodies with the same specificity for the dex epitope. Under the same conditions of immunization, however, IgA anti-dex PFC were mostly single-class secretors. IgA PFC developed in the spleen in highest numbers (equal to IgM), but in Peyer's patches IgA PFC were sevenfold more numerous than IgM. Furthermore, spleen IgG3 anti-dex PFC responses were low compared with spleen IgA and IgM anti-dex PFC responses and appeared only late in ontogeny. The possibility is discussed whether a TH dependence of the IgA anti-dex response and a TH-independent generation of the IgG3 response are responsible for the different pattern of isotype expression.

Sensitive radioimmunoassay for the broad-spectrum antiviral agent ribavirin.

Ribavirin, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxyamide (Virazole; Viratek, Inc., Covina, Calif.), has a broad spectrum of antiviral activity. However, the study of the absorption, metabolism, and excretion of this compound has been limited by the lack of an appropriate assay for ribavirin and its metabolites. Since ribavirin has definite potential for therapeutic use, we developed a radioimmunoassay to measure ribavirin levels in clinical specimens. To prepare an effective immunogen, ribavirin was monosuccinylated and coupled to ovalbumin. The competitive binding radioimmunoassay, in which tritium-labeled ribavirin and rabbit antiribavirin serum were used, was quantitative for ribavirin at concentrations of 1 pmol/100 microliter in urine or plasma samples. The rabbit antibody cross-reacted with the major metabolite of ribavirin, 1,2,4-triazole-3-carboxamide, at a low level (2 to 5%) which did not interfere with ribavirin binding until concentrations of 1,2,4-triazole-3-carboxamide 10- to 100-fold higher than ribavirin were present in mock samples, a condition not present in biological specimens. We used the ribavirin radioimmunoassay to determine the ribavirin concentration in mouse plasma after intraperitoneal administration, in the sera of adults from Sierra Leone after oral or intravenous administration for treatment of suspected Lassa fever, and in the sera of children in the United States after small-particle aerosol administration. Our experience with the radioimmunoassay indicates that it is sensitive, accurate, and reproducible. The assay will permit studies leading to a better understanding of the pharmacology and pharmacokinetics of this potentially useful antiviral drug.

Age-dependence of the IgA anti-alpha (1 leads to 3) dextran B1355 response in vitro.

The magnitude of the Balb/c mouse IgA anti-alpha (1 leads to 3) dextran B1355 (anti-dex) response in vivo was recently found to be markedly T-cell-dependent and age-dependent. This report demonstrates that the in vitro IgA anti-dex response by mesenteric lymph nodes (MLN) is highly age-dependent and that there is an age-dependent increase of the background IgA anti-dex plaque-forming cell (PFC) response occurring in the absence of added antigen which correlates significantly with the magnitude of the antigen-stimulated response. In aging mice both background and antigen-stimulated IgA anti-dex responses appeared to be significantly higher in MLN than in spleen cultures. Moreover, it is shown that there is a striking increase with age of natural antibody in the serum of normal Balb/c to alpha (1 leads to 3) glucan determinants, particularly IgA and lesser amounts of IgM and IgG3.

Gluten-sensitive enteropathy. I. The T-dependent anti-A-gliadin antibody response maps to the murine major histocompatibility locus.

We examined the genetic control of the murine humoral immune response to purified A-gliadin, a protein derived from wheat gluten, which is known to cause small intestinal disease in susceptible individuals. Studies with congenic and noncongenic inbred strains of mice revealed that the T-dependent humoral immune response to A-gliadin is under the control of genes mapping to the mouse major histocompatibility complex (MHC). These findings in mice establish a clear linkage between the MHC and the regulation of the immune response to a protein capable of causing human disease.

In vitro studies of the rabbit immune system. VI. Rabbit anti-mouse cytotoxic T effector cells are inhibited by anti-rabbit T cell serum in the absence of complement.

Xenogeneic rabbit anti-mouse cell-mediated cytotoxic activity could be generated by culturing lymphoid cells from mesenteric lymph nodes (MLN), spleen, or peripheral blood of rabbits primed 2 to 8 weeks earlier with mouse tumor or spleen cells. MLN cells, which provided the best source of activity after being cultured with 5 to 10 X 10(6) mitomycin C-treated mouse spleen cells for 4 to 6 days, produced 30 to 90% specific isotope release after 4 to 7 hr incubation with 15Cr-labeled tumor target cells. Xenogeneic cytotoxic activity was primarily H-2 specific and could not be blocked by immune complexes but was abrogated by treatment with goat anti-rabbit thymocyte serum plus complement (ATS + C) before or after culture. Therefore, the activity appeared to be mediated by cytotoxic T lymphocytes (CTL). Furthermore, ATS without C abrogated cytotoxic activity when included in the CTL assay at concentrations of 5 to 15 microliter/10(7) effector cells. The inhibitory activity of ATS was directed to the rabbit effector population and could be absorbed completely by rabbit thymocytes. Antisera to mouse T cells with comparable cytolytic activity in the presence of C did not inhibit murine allogeneic CTL.

Induction of T cell response to haptens coupled to mycobacteria.

A new method for the induction of cellular immune response to commonly used haptens in the absence of detectable antibody response is described. Different haptens were convalently coupled to Mycobacteria and they were injected into guinea pigs in incomplete Freund's adjuvant. Humoral and cellular immune response to haptens were examined at weekly intervals for 5 weeks. Our results show that a significant anti-hapten cellular response was induced and subsequently elicited by both in vivo (skin test) and in vitro (Lymphocyte transformation and macrophage migration inhibition) assays.