Biomedical subjects
Publications and source records attributed to R Sehgal.
The direct lymphocyte cytotoxicity and antibody dependent cell mediated cytotoxicity against Entamoeba histolytica was studied in 3-4 wk old and 8-10 wk old guineapigs. Both these parameters were significantly increased in splenic cells in the older animals. This might be due to maturation of the immune system or to natural infection by related parasite, leading to immunity.
Humoral and cell mediated immune responses were studied in control, infected and immunized-infected mice at different time intervals. The levels of antiporin antibodies were found to be higher throughout the study period in immunized-infected group in which 87.5% protection was observed by mouse potency test. A significant increase in stimulation index of lymphocyte blast transformation as well as delayed type hypersensitivity response was observed in the same group as compared to infected and control group when porins were used as antigens. Using nonspecific mitogens like PHA and Con A the lymphocyte proliferation was maximum in control group whereas a significant depression was observed in infected mice. It is indicated from this study that porins are excellent antigens interacting efficiently with both arms of the host immune systems which could play a role in providing protection against the disease.
Antibodies to group A streptococcal polysaccharide were estimated in the following groups of patients: (I) Patients with uncomplicated streptococcal pharyngitis: 10 patients, followed up for 3 months. (II) Patients with acute rheumatic fever: 8 patients with first attack followed up for one year. (III) Patients with reactivated rheumatic heart disease: 10 patients, followed up for one year. (IV) Patients with chronic rheumatic heart disease: followed up for one year. (V) normal controls without any history of sore throat/fever/vaccination/rheumatic disease: 10 patients followed up for one year. Group (I) patients did not show any significant elevation in anticarbohydrate antibodies by both ELISA and RIA. In the case of (III) and (IV), antibody levels were significantly higher as compared to group (V) and remained so till one year of follow up. In group (II) patients there was no significant rise in antibody levels. There was a good correlation between the ELISA and RIA used to detect the antibody levels. These findings suggest that the use of ELISA to detect anticarbohydrate antibody can be of help in diagnosing cases of rheumatic heart disease (both acute and chronic RHD).
Dot-enzyme linked immunosorbent assay (Dot-ELISA) used for the serodiagnosis of both intestinal and extraintestinal amoebiasis, showed positivity in 94 per cent patients of amoebic liver abscess and 87.5 per cent of intestinal amoebiasis. Only one of the 18 normal controls was positive by Dot-ELISA test. This test showed good correlation with indirect haemagglutination test. As it is simple and easy to perform, the test appears to have great potential for the specific diagnosis of amoebiasis in peripheral hospitals and also at the field level where sophisticated immunodiagnostic facilities are not available.
Excretory/secretory (E/S) and somatic antigens prepared from third stage infective larvae of Ancylostoma duodenale were evaluated for the diagnosis of human hookworm infection by enzyme-linked immunosorbent assay (ELISA). Taking the mean absorbance plus 2 standard deviations (SD) of normal serum as the cut-off value, the positivity rates in 30 hookworm cases were 97% and 93% respectively. False positivity with E/S antigen was 8-20% in 61 control subjects; with somatic antigen it was slightly lower. In contrast, when the mean absorbance value plus 2 SD of control groups with other parasitic infections was taken as cut-off point, the positivity was 93% with E/S antigen and 43% with somatic antigen, indicating the superiority of E/S antigen. Percentage positivity declined after treatment of hookworm cases. No relationship was found between ELISA reactivity and severity of infection.
Total immunoglobulin E (IgE) and specific IgE were assayed by a radioimmunosorbent test and a reverse enzyme immunoassay in patients with hookworm infections before and after treatment. A total of 77 subjects (30 patients with hookworm infections and 47 subjects as controls) were studied. Both specific and total IgE levels in serum and jejunal juice were raised in hookworm patients. There was a significant decrease in IgE levels after therapy. Total IgE levels were raised in other nematode infections, but specific IgE levels were low. The reverse enzyme immunoassay for specific IgE was highly specific (96%) and sensitive (100%) and may be used in the serodiagnosis of hookworm infections.
To investigate the involvement of immune complexes in the pathogenesis of cerebral malaria, a comparative study between Plasmodium berghei infected Swiss albino mice and BALB/c mice was conducted. Rise in parasitemia was found to be same with differences in manifestation of disease and mortality, level of immune complexes and histopathology. Increased parasitized red cells with swelling of endothelial cells in the brain capillaries along with increased levels of circulating immune complexes were observed in the BALB/c mice.
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The authors report a case of a child with chronic diarrhea due to Cryptosporidium. The child had also hemolytic uraemic syndrome. Cryptosporidium oocysts were identified by the modified Ziehl-Neelsen technique.
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