Retinoblastoma discordance in families with twins

Retinoblastoma has an increased inheritance risk of germline RB1 mutations in offspring and siblings, especially twins. Three families, each having one retinoblastoma-affected twin, were selected for genetic analysis and DNA profiling. Germline RB1 mutations were found in all probands. DNA profiling carried on similar-looking twins of families I and II, proved them to be fraternal. This study demonstrates the importance of genetic analysis of RB1 gene for risk prediction in retinoblastoma families. It also emphasizes that DNA profiling is a mandate for genetic screening of families with twins, thus adding a new dimension in counseling of retinoblastoma.

Field rats form a major infection source of leptospirosis in and around Madurai, India.

AIMS: To determine the seroprevalence of leptospires and to isolate Leptospira spp. from field rats and bandicoots in and around Madurai. MATERIALS AND METHODS: Thirteen rats and five bandicoots were trapped alive from fields in and around Madurai. Blood samples were tested for anti-leptospiral antibodies by microscopic agglutination test while the urine and kidney samples were used for isolation of leptospires. The isolated leptospires were tested for pathogenic status (13 degrees C test and PCR) followed by serological and genetic characterization. RESULTS: Serology revealed the presence of anti-leptospiral antibodies in 58% (7/12) of field rats and leptospires were isolated from two urine and six kidney samples. The bandicoots were negative in both serology and culture. Analysis of the isolates from field rats revealed that all the isolates were pathogenic except for one, which was further confirmed by serological and genetic characterization. Six of the seven pathogenic isolates were identified as L. interrogans serogroup Autumnalis serovar Akiyami A and one as L. borgpetersenii serogroup Javanica serovar Veldrat Batavia 46. CONCLUSIONS: Serology and isolation reveals that field rats are major natural carriers and shedders of leptospires in and around Madurai.

Strain dependent & selective modulation of murine humoral immune response by carrageenan.

Carrageenan (CGN), a polygalactan extracted from red algae, induced 90 per cent suppression of antibody response to sheep red blood cells in Balb/C strain as compared to the untreated controls. Whereas the treatment failed to induce suppression in C57BL/6 strain. The observed suppression of antibody response was significant on all days tested (up to 40 days) and the suppression induced by CGN was real and not due to any direct effect on antigen or on the assay system followed. On the other hand, as evident from foot-pad thickness, the delayed type hypersensitivity (DTH) was unaltered in Balb/C strain after CGN treatment.

Immunological status of patients of Eales' disease.

To test the hypothesis that altered immune reactivity to an extraneous agent might lead to primary retinal perivasculitis, a study was undertaken to determine the serum immunoglobulin levels, T lymphocyte subsets, antibody responses to BCG and 'S' antigen, and lymphoproliferative response to mitogens. No difference was observed in these parameters between patients and controls. Both Mantoux positive and negative conditions existed in patients with Eales' disease. Mantoux positive patients showed a higher level of lymphoproliferative response in vitro to PPD than Mantoux positive controls, indicating the presence of two populations among Eales' patients.

Protective immunity induced by porin against Salmonella infection in mice.

Porin, a major outer membrane protein was purified from Salmonella typhimurium and its immune potential was studied in mice. Active immunization with porin induced about 45 per cent protection to an intravenous challenge with 10LD50 of S. typhimurium. Further, in porin immunized mice significant level of anti-porin antibodies and DTH reaction were detected. Attempts were also made to improve the immune potential of porin. Freund's complete adjuvant when mixed with immunogenic doses of porin enhanced the anti-porin antibody titre. However, it could not improve the protective ability of porin. On the other hand, porin when injected along with lipopolysaccharide (LPS) induced a higher level (55% survival with 50LD50) of protection than porin or LPS alone. This finding was also substantiated by the significantly reduced in vivo growth of challenge organisms in mice immunized with porin plus LPS. These results indicate that porin is a protective antigen and LPS significantly enhances the protective ability of porin.