Circulating antibodies to mouse monoclonal immunoglobulins in normal subjects--incidence, species specificity, and effects on a two-site assay for creatine kinase-MB isoenzyme.

With a two-site CK-MB assay, we screened serum samples from 1008 blood donors for the presence of antibodies to mouse monoclonal immunoglobulin. These antibodies were capable of cross-linking the labeled antibody with the solid-phase antibody in the two-site assay, thus generating a falsely high apparent CK-MB concentration. In 92 (9.12%) of the blood donors tested, apparent CK-MB concentrations of 10-1000 micrograms/L decreased to less than 3 micrograms/L when re-assayed with non-immune mouse serum (10 mL/L) included in the assay reagent. We tested the ability of non-immune sera from other animal species to lower the concentration of apparent CK-MB in 58 of the 92 samples. Bovine and ovine serum were almost as effective as mouse serum; feline, canine, and rabbit serum were less effective. Of the samples tested, 12% (1.1% of the original population screened) showed apparent CK-MB values that either were not depressed by bovine serum or were only partly depressed. We discuss the possible etiology of these antibodies in normal subjects and recommend that all mouse monoclonal two-site assays should contain non-immune mouse serum (or a suitable "irrelevant" mouse monoclonal antibody) to prevent false-positive results.

Candidacidal activity of mouse macrophages in vitro

Mouse peritoneal macrophages were infected in vitro with Candida albicans, and the phagocytic and candidacidal activities were estimated by microscopic examination of Giemsa-stained cells. Activated macrophages obtained from either BCG-vaccinated animals or by in vitro exposure of normal macrophages to phytohemagglutinin-induced lymphokines exhibited higher phagocytic and candidacidal activities than did normal macrophages. However, activated macrophages obtained by in vitro exposure of macrophages to candida-induced lymphokines exhibited the highest phagocytic and candidacidal activities. The incorporation of immune mouse serum into the culture medium also enhanced the phagocytic and candidacidal activities of the normal macrophages but failed to improve the function of the activated macrophages. These results suggest that both activated macrophages and antibodies may be required for controlling candida infections in mice.

THE PASSIVE TRANSFER OF ACQUIRED RESISTANCE TO LISTERIA MONOCYTOGENES

Five methods have been used in an effort to reveal an antibody that could account for the features of acquired resistance to Listeria monocytogenes: (a) a comparison of the growth rates of Listeria in the spleens of mice infused repeatedly with normal or immune mouse serum; (b) measurement of peritoneal clearance of Listeria in the presence of normal or immune mouse serum; (c) the survival rate of Listeria in monolayers of mouse macrophages infected in the presence of normal or immune mouse serum; (d) the effect of injecting urea extracts of spleens and peritoneal macrophages of normal or immune mice on the survival and growth of Listeria in recipient animals; (e) a comparison of survival rates in lethally infected mice following the passive transfer of cells and serum from normal or immune donors. The only evidence of passive protection was obtained when intact living cells from immune donors were used for transfer under conditions which permitted them to interact with the parasite population.