Antigen-specific stimulation of histamine releasing factors in diisocyanate-induced occupational asthma.

Diisocyanate-induced asthma differs from occupational asthma (OA) caused by protein allergens in that specific IgE antibody responses are rarely identified. To investigate the immunopathogenesis of diisocyanate asthma, diisocyanate-exposed workers were evaluated for in vitro production of antigen-specific mononuclear cell-derived histamine releasing factor (HRF). The mean HRF response to diisocyanate-HSA antigens was significantly greater in patients with OA than in diisocyanate-exposed asymptomatic subjects (p < 0.05). No association was found between HRF and diisocyanate-specific antibodies. Analysis of HRF production by subpopulations of peripheral blood mononuclear cells (PBMC) showed that lymphocytes and adherent cells were major sources of both spontaneous and antigen-stimulated HRF. The results suggest that antigen-specific HRF produced by PBMCs are an important biomarker for diisocyanate-induced asthma. This is the first report of hapten-specific stimulation of PBMCs resulting in HRF production.

The low prevalence of occupational asthma and antibody-dependent sensitization to diphenylmethane diisocyanate in a plant engineered for minimal exposure to diisocyanates.

BACKGROUND: Diisocyanate chemicals are leading causes of occupational asthma (OA). METHODS: We conducted a cross-sectional study of 243 workers exposed to diphenylmethane diisocyanate (MDI) in a urethane mold plant that had been designed to minimize MDI exposure (levels were maintained below 0.005 ppm and were continuously monitored). All participants were screened by questionnaire and tests for serum antibodies to MDI-human serum albumin (HSA). On the basis of questionnaire responses, diagnoses were derived that included OA; non-OA; work-related and non-work-related rhinitis; and lower respiratory irritant responses. Serial peak expiratory flow rate studies were performed for 2 weeks in 43 workers with and in 23 workers without lower respiratory symptoms. RESULTS: Results of serial peak expiratory flow rate studies were abnormal in 3 (33%) of 9 workers with OA, in 2 (50%) of 4 with non-OA, and in 2 (9%) of 23 case control subjects. A significant association was found between peak flow rate variability and a questionnaire asthma diagnosis (chi 2 p < 0.002). Physicians confirmed three cases of OA, one of which occurred in a control worker who was free of symptoms. In all three cases asthma symptoms remitted after the worker left the workplace. Serum specific IgE and IgG levels were elevated in 2 of 243 workers, one of whom was prick test positive to MDI-HSA and had had cutaneous anaphylaxis after MDI exposure. CONCLUSIONS: On the basis of these cases, specific work activities associated with exposure to MDI were identified and corrective measures were instituted. Strict control and monitoring of ambient MDI exposure was associated with a low prevalence of specific sensitization to MDI and a lower than expected prevalence of OA.

Monoclonal antibody for the detection of Clostridium botulinum type A toxin.

Hybridomas producing monoclonal antibodies against type A Hall strain Clostridium botulinum toxin were generated by fusing mouse myeloma cell line P3-X63-Ag8.653 with spleen cells of Balb/c mice immunized with C. botulinum type A toxoid. The monoclonal antibody from one hybridoma, identified as No. 424, was selected from 61 others for its high antibody titre. This monoclonal antibody was used in a double-sandwich enzyme-linked immunosorbent assay (ELISA) system to detect type A toxin in culture fluids and in foods. The monoclonal antibody did not react with either C. botulinum toxin types B, C, D, E and F or with other clostridial species tested. This particular monoclonal antibody (No. 424) did not neutralize type A toxin in the mouse bioassay procedure but detected approximately 10 mouse lethal doses of type A toxin/ml culture fluid. Monoclonal antibody and rabbit antitoxin to type A C. botulinum toxin were useful in a double-sandwich ELISA for the rapid and specific detection of type A toxic fluids in culture and in food samples.

Suppression of B16 melanoma lung colonization by syngeneic monoclonal antibodies.

Syngeneic monoclonal antibodies (MAbs) were produced to B16 melanoma by hybridization of spleen cells from B16-F1 or B16-F10 tumor-bearing C57BL/6J mice. Two antigens were identified by the immunofluorescence reactions of anti-F1 MAbs, 2G10 (IgG1) and 3C10 (IgM). Both antigens are membrane associated in 97-99% of fixed F1 and F10 cells and are cross-reactive with normal syngeneic thymocytes, and other normal and transformed cultured mouse cells. An anti-F10 Mab, 3E9 (IgG3), reacts with a membrane antigen found in about 40% of F1 and F10 cells and in all transformed mouse cells tested, but was not found in normal cells. The 3C10 and 3E9 antigens are shed into the medium of cultured cells. 125I-Labeled membrane components of Mr 48,000 and 40,000 (3C10) and 25,000 (3E9) were immunoprecipitated. Some 3C10 immunoprecipitates also contained components of Mr 25,000 and 15,000. The three MAbs were tested for suppression of lung colonization by B16-F1 and B16-F10 metastatic variants in C57BL/6J mice. MAbs were injected 1 day prior to and 1 week after injection of tumor cells. 2G10 was highly suppressive for both B16-F1 and B16-F10 cells. 3C10 and 3E9 were suppressive for B16-F10 cells but were nonsuppressive and enhancing for B16-F1 cells (P less than or equal to 0.05). A novel immunotherapy model was tested. Delayed hypersensitivity was selectively induced to the 3C10 MAb in C57BL/6J mice by sensitization with lipid-conjugated purified MAb. Sensitized mice were injected with B16 cells and MAb to determine whether a cellular reaction with cell bound MAb in vivo could be suppressive for tumor cells. The treatment was suppressive for B16-F1 lung colonies, but caused augmentation of lung colonies from B16-F10 cells (P less than or equal to 0.05).

Population genetics of Aa and Ab immunoglobulin allotypes in wild rabbits of south-eastern Australia. I. Allotype frequencies.

Aa and Ab allotype frequencies have been investigated in wild rabbit populations throughout Victoria and South-east South Australia. The overall mean allele frequencies for thirty-three populations are 0-53:0-12:0-36 for a1:a2:a3 and 0-72:0-22:0-05 for b4:b5:b9. The b6 allele was not found anywhere. The a1 frequency has been found to increase in proportion to increases in mean annual rainfall. While considerable variations exist in allotype and allele frequencies from area to area, the relationships a1 greater than a3 greater than a2 and b4 greater than b5 greater than b9 are almost always observed. The results are discussed in terms of the historical origins of Australian wild rabbits and possible genetic mechanisms to explain the maintenance of allotype 'hierarchies' in large populations breeding at random.