Intracellular Bacterial Infection and Invariant NKT Cells

The invariant (i) natural killer (NK)T cells represent a unique subset of T lymphocytes which express the V alpha14 chain of the T cell receptor (TCR), that recognizes glycolipid antigens presented by the nonpolymorphic major histocompatibility complex (MHC) class I-like antigen presentation molecule CD1d, and they participate in protection against some microbial pathogens. Although iNKT cells have originally been regarded as T cells co-expressing NKR-P1B/C (NK1.1: CD 161), they do not seem to consistently express this marker, since NK1.1 surface expression on iNKT cells undergoes dramatic changes following facultative intracellular bacterial infection, which is correlated with functional changes of this cell population. Accumulating evidence suggests that NK1.1 allows recognition of "missing-self", thus controling activation/inhibition of NK1.1-expressing cells. Therefore, it is tempting to suggest that iNKT cells participate in the regulation of host immune responses during facultative intracellular bacterial infection by controlling NK1.1 surface expression. These findings shed light not only on the unique role of iNKT cells in microbial infection, but also provide evidence for new aspects of the NK1.1 as a regulatory molecule on these cells.

Inquérito soro-epidemiológico antilistéria em Uberaba, MG / A seroepidemiological investigation of listerosis in Uberaba, MG

From a total of 445 individuals, 17.1 per cent had antibodies against L. monocytogenes detected by the agglutination tube test. They were separated in seven groups: bloods donnors (n = 50), Hospital visitors (n = 40), frigorific workers (n = 28), aviculture workers (n = 87), herdsman (n = 31), agriculture students (n = 60) and street-sweepers (n = 51). L1/2a serotype was predominant. Individuals from urban areas (19.5 per cent) and those who had less contact with animals (21.7 per cent) had significantly positive serology when compared with individuals from rural areas (9.4 per cent) and those who had close contact with animals (13.2 per cent). The overall picture is individuals of more specialized occupations had more frequently (25.9 per cent) anti listeria antibodies similar to the results observed in developed countries where listeriosis is a public health problem in urban areas.

Study of interactions between Listeria monocytogenes and experimental tumors

OBJECTIVE--to verify the effects of Listeria monocytogenes (LM) inoculation in the survival of animals bearing Ehrlich's tumor. KIND OF STUDY--experimental. Animals-isogenic mice, Balb/c, female, 19-21 g. Tumor-Ascitic Ehrlich's tumor, dilution of 5 x 10(5) cells/0.1 ml. Bacteria-LM serotype 4a, solution with 7 x 10(3) bacteria (standard sub-lethal dose). Intervention-a) inoculation of LM in mice bearing Ehrlich tumor at the same time as ascitic cells transplantation. b) inoculation of LM seven days before and, again, seven and fourteen days after ascitic cells transplantation. c) to study the effect of using ampicillin 100 mg/kg, im, simultaneously with the inoculation of Ehrlich tumor and LM organisms and, again, 3, 5, 7, 14, 21 and 30 days after the ascitic cells transplantation. ANALYSIS--Chi-square test; p < 0.05 RESULTS AND CONCLUSION--LM increases significantly the survival of mice bearing Ehrlich tumor even when only one inoculum of viable LM was used, seven days before or seven days after the ascitic cells transplantation. The use of ampicillin after the inoculation of LM and tumor transplantation does not alter the survival of mice