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.

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Summary. Tlit* ability of rahhit lf;G tn localize in Follicles of rat lympli nodes (Iifterologoiis sysU-m) lias IH'CII shown to hv tint-to tlit* i' V fragiiifnt. Of tlic-r»l)bit IyG subiinits e\:imiiu;tl, llie H chain .uul Fc fraynK-iit showed folticular localization in rats, while tlie L chain and Fa!) friij;nient did not. Two Iarf:c pfplidcs from the Fc region of tlie molecule, C3 and C4, also showed follicithir locali/ation.Human seriini albumin showed follicuhir localization in rats only when it was couiplexed with rabbit anti-hnmiin senm) albumin intact IKG. Complexes of hnnian serum nlbumin with rabl)it anti-hnman senim alhtnniii Fab fragment did not go to the follicles.When major Mibtmits of rabbit IKG were injected into rabbiLs (homologous system) results were qualitatively the same as those obtained in rats, with one exception. Rabbit Fab localized in follicles of rabbit nodes. It was also found the rat Fab localized in rat follicles.Purified rat IgM has been shown to localize well in rat follicles. All substanee.s examined have shown medullary localization.

Summary. Studies on the retention of '-''I-labelled rat and rahliit imniunoj,'lohulins and subunits thereof in rat popliteal nodes indicate that Uie Fc fragment of IgC is important for maintaining a relatively high concentration of this immimoglohulin in lymph nodes.After footpad injections of the inununoglobidins ami siibunits. an appro.\imate c-orrelation wiLs found between the initial rate of disappearance from the feet and the molecnlar size of the substances injected. Tiu-s suggested tliat a major factor involved in removal of substances from rat footpads is their rate of diffusion. No correlation with molecular weight was found in the retention pattern of immunoglobulin subunits In tlie popliteal nodes which dntined the footpads. Rabl)it Fc fragment was retained 50 times better than rabbit Fab fragment in rat nodes 3 days after injection. Rabbit H cbains were retained bt^tter tlian rabbit L chains.A peptide from the Fc region of rabbit heavy chains, C3, showed high retention in rat nodes and was retained Ijetter than IgG but not as well as Fc. Rat IgG and IgM were both retained Ijettor than rat Fab in rats. Hiunan serum albumin complexes with rabbit anti-human serum albumin IgC was retained at least 10 times better by rat nodes than human seniru albumin alone. Human senim albumin Ijoimd to rabbit anti-human senun albiuiiin Fab was retained only about twice as well as human serum albumin alone.INTRODUCTION.

Summary. A mixed breed of rabbits bred at Monash University has been shown to produce electmphorpticaHy nioniKlisperse (homogeneous) antibodies to tlir group specific carhohydrates of streptococci. All rabbits given primary immunization with Croup B or Clroup C streptowccal vaccines showed more than one liomogeneoiis imnitmoglohulin when sera were examined by cellulose acetate electrophoresis. These homogeneous components were shown to be antibodies to the group specific carbohydrate. Antibody levels to the carbohydrate varied from 1 to 10 mg/nil antisenim. Fractionation of anti-Group B .'iennn by anion exchange chromatogruphy showed that heterogeneous ;inti-strfptococcal iintiljody was also present, but was specific for celhilar con.stituents other than the group carbohydrate, Monash rabbits immunized with non-streptococcal antigens have shown a normal heterogeneous antibody response.