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Biomedical subjects

T Pang

Publications and source records attributed to T Pang.

At least 109 records · Page 6Linked to original sources
PubMed1983

Delayed-type hypersensitivity (DTH) response to dengue virus in mice: effect of route of sensitization and splenectomy.

This study was designed to determine the role of the sensitization route and the spleen in the development of delayed-type hypersensitivity (DTH) to dengue virus in mice. DTH was measured by footpad swelling response. Strong but transient DTH was produced in cyclophosphamide (CY) pretreated mice sensitized subcutaneously (s.c.) or intravenously (i.v.) with dengue virus type 4. Subcutaneous inoculation of virus in incomplete Freund's adjuvant (IFA) further enhanced the DTH elicited. The time course of DTH generated by s.c. and i.v. sensitization were similar with the peak reactivity seen on day 6 after sensitization. Poor DTH was observed in mice given an i.p. inoculation even when CY and/or IFA were used. Intracerebral (i.c.) inoculation also sensitized mice poorly. Splenectomized mice showed enhanced DTH response when compared to intact mice. In contrast to intact mice, pretreatment of splenectomized mice with CY did not alter the DTH level. Splenectomized mice inoculated s.c. with virus in IFA showed poorer DTH than mice sensitized with virus alone.

Animals↗
PubMed1983

Demonstration of a cytotoxin from Campylobacter jejuni.

A 48-hour culture filtrate of Campylobacter jejuni was found to produce cytopathic effects on three human cell lines--that is, HeLa, MRC-5 and Hep-2. The cytopathic effects observed include cell rounding, loss of adherence and cell death after 24-48 h of incubation. Such morphological changes were observed with eight of the eleven strains of Campylobacter jejuni isolated from the blood/stools of patients who suffered from either acute gastroenteritis or septicaemia. The toxic factor did not retain its activity after treatment at 100 degrees C for 30 min. Trypsinisation of the filtrate totally abolished its toxic activity thus indicating that it was probably protein in nature. It is most probably an extracellular toxin as bacterial sonicates did not produce any toxic effect. This study reports the finding of toxic factor(s) in the culture filtrate of Campylobacter jejuni which is cytotoxic to human tissue culture cells.

Adult↗
PubMed1983

Significance and value of the Widal test in the diagnosis of typhoid fever in an endemic area.

The diagnostic value of the Widal test was assessed in an endemic area. The test was done on 300 normal individuals, 297 non-typhoidal fevers and 275 bacteriologically proven cases of typhoid. Of 300 normal individuals, 2% had an H agglutinin titre of 1/160 and 5% had an O agglutinin titre of 1/160. On the basis of these criteria a significant H and/or O agglutinin titre of 1/320 or more was observed in 93-97% of typhoid cases and in only 3% of patients with non-typhoidal fever. Of the sera from typhoid cases which gave a significant Widal reaction, the majority (79.9%) showed increases in both H and O agglutinins and 51 of 234 (21.8%) of these sera were collected in the first week of illness. The significance and implications of these findings are discussed.

Agglutination Tests↗
PubMed1982

Induction and characterization of delayed-type hypersensitivity to dengue virus in mice.

Delayed-type hypersensitivity (DTH) to dengue virus type 4 in mice is described. The DTH reaction (measured by footpad swelling) was maximal at 24 hr after challenge and was enhanced significantly when mice were pretreated with cyclophosphamide. The response was maximal six days after infection with an immunizing dose of approximately 10(7.3) 50% lethal doses per mouse. Histologic examination of the test footpad showed a predominantly mononuclear cell infiltrate at 24 hr after challenge. fibrin deposition was also noted. DTH reactivity was transferable to normal mice by injection of immune spleen cells but not of immune serum. The DTH reaction was apparently specific for dengue virus type 4 because significantly lower responses were detected when dengue virus types 1-3 and Japanese encephalitis virus were used as challenge antigens in mice infected with dengue virus type 4. The probable importance and significance of these findings in relation to the host immune response and the pathogenesis of dengue virus infection are discussed.

Animals↗
PubMed1979

Serum complement (C3 and C4) levels in the Malaysian adult population.

Serum C3 and C4 values were determined in 236 normal adults of three racial groups, using the single radial immunodiffusion techniques. The C3 levels varied from 47 to 119 mg/dl and C4 levels from 16 to 66 ml/dl (mean +/- 2SD). The values were found to be comparable to the normals reported in some Western series. No significant differences in the levels related to sex and race were found.

Adolescent↗
PubMed1977

Specificity or affinity of cytotoxic T cells for self H-2K determinants apparently does not change between primary and secondary responses to ectromelia virus infection.

Lysis of virus-infected target cells by virus-specific cytotoxic T cells occurs where donors of T cells and targets share either H-2K or H-2D genes. The effect of four H-2K mutations on virus-induced antigens recognized by cytotoxic T cells from in vitro secondary response to infection was studied. B10.A(5R) cytotoxic T cells (which share the K end of H-2 with the mutant strains, except for the mutated gene(s)) efficiently killed virus-infected macrophage targets from mutant strains B6-H-2bg1 and B6-H-2bg2, were less effective against B6-H-2bh and did not appear to be cytotoxic for B6.C-H-2ba target cells. Conversely, B6-H-Ibg1 and B6-H-2bg2 cytotoxic T cells were more effective in killing virus-infected B10.A(5R) macrophages than B6-H-2bh and B6.C-H-2ba cytotoxic cells respectively. In addition, B6-H-2bg1 and B6-H-2bg2 cells appeared to be only slightly different from wild-type with respect to the interaction between virus-infected cells and T cells. The data obtained suggested that virus-induced antigenic patterns on infected B6.C-H-2ba (mutant) cells are more different antigenically from those on wild-type cells than are those on infected cells from the other mutants, B6-H-2bh, B6-H-2bg1 and B6-H-2bh2. This agrees with previous data using primary cytotoxic T cells and thus suggests that no detectable change in the affinity or specificity of cytotoxic T cell receptors occurs between primary and secondary responses to infection. These findings are also discussed in relation to the exclusion of T cells with receptors for H-2K determinants that are common to the mutants and wild-type, from the response to virus-infected self cells.

Animals↗
PubMed1977

Requirements for stimulation of T cell responses against virus-infected cells: nature of ectromelia virus-infected cells capable of stimulating cytotoxic T cells in a secondary response in vitro.

The nature of infected stimulator cells in the in vitro secondary cytotoxic T cell response to ectromelia infection was investigated. It was found that macrophages were better stimulator cells than spleen cells. B cells (Ig-positive cells) were superior to T cells (Ig-negative cells) both on a relative proportion and on a cell-to-cell basis. Concanavalin A and lipopolysaccharide-stimulated lymphocytes were also effective stimulator cells but appeared to be slightly inferior to spleen cells. Spleen cells depleted of Ia-positive cells were markedly inferior to normal spleen cells as stimulators. It was also found that primary and secondary cytotoxic T cells were largely Ia-negative. These findings are discussed in relation to the likely events during T cell responses to infection in vivo.

Animals↗