Cent Of Leukocytes Research Articles

Characterisation of leucocytic somatic cells in bovine milk

The mammary gland is of cutaneous origin with stromal leucocytic infiltrates and it excretes leucocytes in the milk. Milk T lymphocytes are highly enriched by sedimenting milk somatic cells in a 43 per cent preformed Percoll gradient. Thirty to 54 per cent of leucocytes, harvested from the upper Percoll band, belong to CD2+ CD3+ T lymphocytes. These milk T lymphocytes are mature CD4+, or CD8+ single positive T cells, expressing CD44, CD26, and 131 integrin, but not Lam-1. Milk T lymphocyte subsets may play an important role in regional immunosurveillance of the mammary epithelia and stroma. Selective mechanisms may account for the trafficking of this activated, memory T lymphocyte subset in the gland.

Modulation of human neutrophil adherence by oral bacteria.

Polymorphonuclear neutrophils (PMNs) comprise over 90 per cent of leukocytes in the oral cavity. Although these phagocytic cells have primary defence roles in the gingiva, their stimulation by micro-organisms may also cause substantial tissue damage due to the release of lysosomal enzymes and oxygen radicals. Adherence of PMNs to the endothelium and their subsequent diapedesis and egress to areas of infection are considered early vital events in the inflammatory process. In this study, oral bacteria were screened to determine their direct effects on PMN activation using an in vitro method of measuring PMN adherence to Dacron fibres. Most of the bacteria investigated increased PMN adherence, indicating their potential to cause tissue damage through the release of PMN lysosomal enzymes and other products. In contrast, Bacteroides species suppressed PMNs, indicating their ability to circumvent the phagocytic cells, thus gaining a potential advantage in dental colonization. The modulatory effects of oral bacteria on PMN activation may have significant roles in the immunopathogenesis of oral disease.

Effect of immunisation on the early influx of neutrophils during staphylococcal mastitis in ewes

The neutrophil influx into mammary secretions was studied in unimmunised, and in systemically and locally immunised, lactating and non-lactating ewes experimentally infected with Staphylococcus aureus. Systemic immunisation was effected by subcutaneous injection of live bacteria or by intramuscular injection of killed bacteria in Freund's incomplete adjuvant. The initial inflammatory response to infection of the mammary glands of systemically immunised lactating ewes was at first comparable with that for unimmunised, lactating ewes. However by eight hours after challenge the leucocyte concentrations were lower in systemically immunised ewes. In non-lactating ewes immunised with live vaccine, higher leucocyte concentrations and higher proportions of neutrophils were recorded four hours after infection (hpi) than for unimmunised ewes or ewes immunised with killed vaccine. Prior local immunisation, by unilateral infusion of killed bacteria into mammary glands, enhanced the initial neutrophil influx in comparison to infection of unimmunised contralateral glands of non-lactating ewes by four hpi. For these animals the proportion of neutrophils in washings from immunised glands were significantly greater than for unimmunised glands four and six hpi. In two of three locally immunised lactating ewes there was a larger neutrophil influx into secretions of locally immunised glands than unimmunised glands six hpi. Neutrophils comprised more than 93 per cent of leucocytes from all infected glands by eight hpi. The results suggest that differences in the rate of influx of neutrophils into infected mammary glands of immunised and unimmunised ewes could be attributed to immunological enhancement of neutrophil recruitment or to limitation of toxic damage to tissues with consequently diminished neutrophil invasion.

INVESTIGATION ON THE METHOD OF LEUKOCYTE SEPARATION

The establishment of the excellent leukocyte separation method is at first required in biochemical studies of leukocyte enzymes. The leukocyte separation method with highmolecular dextran (average M.W. 228, 000) was examined following the studies of phytohemagglutinin and Gam Acasia methods formerly reported. Several kinds of concentrations of dextran solution, mixing ratios of dextran solution and blood, and influence of temperature were investigated in order to establish optimal conditions i.e. comparative leukocyte yields, convenience, and minimal erythrocyte contaminations. It was found that the condition of mixing blood and six per cent dextran solution in the following volume ratio (B: D) 6: 1 was most suitable. The mean of leukocyte yields was 68.3±0.55 and erythrocyte contaminations were below 94 per cent of leukocytes. The nature of separated leukocytes showed no significant changes comparing with that of fresh capillar blood, by Giemsa staining, supravital staining, phagocytosis-test of indian ink and differentials. These indicate that leukocyte injuries with dextran method are minimal and separated leukocytes are usable for biochemical studies. The dextran method is better than the phytohemagglutinin and Gam Acasia methods in regard to leukocyte yields and convenience.