Cell-free Antigens Research Articles

Minimum number of bacteria needed for antigen detection by counterimmunoelectrophoresis: in vivo and in vitro studies.

Threshold concentrations of Streptococcus pneumoniae type 3, Haemophilus influenzae type b, and Streptococcus sp. group B type Ib required for positive counterimmunoelectrophoresis reactions were determined in vivo and in vitro. Animals were infected intraperitoneally with various concentrations of microorganisms: adult mice with S. pneumoniae, suckling rats with H. influenzae, and 3-week-old mice with Streptococcus sp. group B. At 24 h after infection a minimum blood concentration of 10(3) colony-forming units (CFU)/ml was needed for S. pneumoniae or H. influenzae before antigen was detected in the serum. A minimum concentration of 10(6) CFU/ml was needed for Streptococcus sp. group B at 10 h after infection. Larger threshold concentrations (10(4) CFU/ml for S. pneumoniae, 10(5) CFU/ml for H. influenzae, and 10(7) CFU/ml for Streptococcus) were required in broth-grown cultures before cell-free antigens could be demonstrated by counterimmunoelectrophoresis in the medium. Marked levels of antigen release by group B streptococci were observed as the cultures entered early stationary phase. This study provides evidence of a long-accepted, though poorly substantiated, hypothesis that a threshold concentration of microorganism is necessary before counterimmunoelectrophoresis reactions become positive. Counterimmunoelecrophoresis results for clinical specimens should be interpreted cautiously in light of this evidence.

Improved version of the exoantigen test for identification of Coccidioides immitis and Histoplasma capsulatum cultures.

A rapid and simple method for extracting specific cell-free antigens of Coccidioides immitis and Histoplasma capsulatum from agar slant cultures was developed. The extracts were analyzed in immunodiffusion tests for the presence of C. immitis or H. capsulatum specific antigens. These extracts were compared with culture filtrates of brain heart infusion broth subcultures in tests with 32 isolates of C. immitis and H. capsulatum and 13 other fungi which might be morphologically confused with them. The studies showed that the slant extracts were as useful as the culture filtrates and allowed more rapid identification of C. immitis and H. capsulatum. In every case, when an identification was made by conventional morphological methods, the immunological test yielded correlating results. The immunological tests were positive for two isolates that were converted to their yeast forms only after 4 months of study by conventional tests. The new procedure permits the identification of C. immitis and H. capsulatum 2 days after receipt of a pure mycelial-form culture. The test is recommended for the presumptive identification of C. immitis and H. capsulatum cultures.

Destruction of Splenic Transplantation Antigens by a Factor Present in Liver

Summary Intact liver tissue implanted subcutaneously or liver cell suspensions injected subcutaneously sensitized recipient animals to subsequent appropriate skin grafts. Two standardized methods for the preparation of cell-free transplantation antigens, as assayed by accelerated skin graft rejection, were employed for the extraction of antigens from C57BL/6 spleen and liver. Both methods resulted in active sensitizing material from splenic tissue; however, no active antigen could be extracted from hepatic tissue. Incubation of active C57BL/6 splenic antigen for 1 hr at 37°C with C57BL/6 whole liver homogenate destroyed the ability of splenic antigen preparations to sensitize to subsequent skin grafts. Heating the whole liver homogenate to 80°C (10 min) prior to incubation destroyed the ability of the homogenate to inactivate the splenic antigen. Treatment of the liver homogenate with a chelating agent and dialysis of the liver homogenate failed to inhibit its ability to inactivate splenic antigen preparations. These experiments suggest that liver cells apparently contain a material which is capable of destroying the sensitizing ability of the transplantation antigens extracted from splenic tissue. These results further suggest an explanation for the frequently observed inability to prepare from hepatic tissue antigenic material capable of sensitizing to a subsequent skin allograft.