Journal of the Reticuloendothelial Society最新文献

The role of chicken bursal and thymic reticular epithelial cells (REp cells) in the induction of B- and T-lymphocyte differentiation has been investigated using in vitro culture of these cells. Splenic adherent cells were used as controls. Precursor populations were obtained predominantly from embryonic bone marrow or spleen and incubated with REp cell monolayers for 72 hr. Differentiation was assessed by the expression of specific membrane antigens: chicken B lymphocyte-specific antigen (CBLA) and chicken T lymphocyte-specific antigen (CTLA). Bursal REp cells specifically induced approximately 20-30% of the embryonic cells to express CBLA but had no influence on CTLA expression. Conversely, CTLA, but not CBLA, was induced in approximately 20% of the embryonic cells by the thymic REp cell cultures. No effect on the expression of either antigen was observed with the splenic adherent cells. The induced cells correspond to the first stage of B- and T-lymphocyte differentiation found in vivo. The assay system also facilitated the study of shifts in precursor content of various organs with development. Whereas embryonic bone marrow of all ages studied contained both B- and T-lymphocyte precursors, these were not demonstrable in donors after hatching. Use of 12-day embryonic bursa and thymus suspensions as sources of stem cells indicated that precommitment to the B- or T-lymphocyte lineage is irreversible.

To study the nature of reticular epithelial (REp) cells and their role in the specific microenvironments of the chicken bursa and thymus, a method was developed for the in vitro culture of purified preparations of these cells. For comparison, similar cultures of splenic adherent cells were also performed. REp cell-rich bursa medullary follicles and mildly trypsinized thymic fragments were X-irradiated (850 rad) to eliminate remaining lymphocytes and transferred to culture flasks. In bursal cultures, after 2-4 days incubation the basement membrane (BM) encapsulating the follicles disrupted and the immediately underlying epithelial cells grew out as a monolayer. By 10 days, REp cells at the periphery developed cytoplasmic processes; occasionally these cells appeared to "bud-off" and grow as isolated dendritic cells. Thymic REp cells were generally slower to proliferate but formed a monolayer by 10-14 days. Splenic adherent cells developed extensive growth within 4 days. REp cells were distinguished from fibroblasts, when present, morphologically and by their limited phagocytic ability. The former were also periodic acid-Sciffs reagent (PAS)-positive and produced reticulin granules. Bursal REp cells were also positive for a gut-associated mucin, but this may have been bound in vivo prior to culture. Neither T nor B lymphocyte-specific antigens were detectable on the cultured REp cells or splenic adherent cells, but they were all rich in cytoplasmic actin. A major feature of REp cells to emerge in this study was the obvious presence of subpopulations of these cells, which raises important questions as to their exact nature and lineage. The accompanying paper details the ability of the bursal and thymic REp cell cultures to induce B-or T-lymphocyte differentiation, respectively, in vitro.

The simultaneous injection of carbaryl and colloidal carbon phagocytized by the reticuloendothelial cells results in competition between the two substances in favor of the carbon particles. Experiments with opsonized carbaryl suggest that the decrease in carbaryl blood clearance by the colloid is mediated by a depletion of serum opsonins. Following blockade, the liver carbaryl uptake was depressed in the control group (17%), while it was increased in the opsonized group (12%). With all preparations of carbaryl, opsonized or non-opsonized, colloidal carbon produced a slight and variable increase in carbaryl uptake by the spleen and lungs. These results indicate that, besides the uptake of carbaryl by the hepatocytes, other clearance sites must also be considered such as the Kupffer cells and other liver sinusoidal cells. Moreover our results show that intravenous administration of carbaryl induces a state of phagocytic depression as indicated by impaired intravascular phagocytosis and depressed hepatic uptake of the reticuloendothelial (RE)-test colloidal suspension. The results obtained from injection of opsonized colloidal particles during carbaryl-induced RE-depression, and the fact that carbaryl and carbon are both opsonized by the same serum factor, suggest that the mechanisms of RE-blockade involve selective hepatic and splenic macrophage failure and depletion of serum opsonins. According to our enzymatic investigation, this failure of the RE system to incorporate colloids during carbaryl--RE-blockade could be due to a defect in the activity of macrophage membrane-bound serine esterase.

The effectiveness of liposome-encapsulated cephalothin was compared with free cephalothin for the treatment of mice experimentally infected with Salmonella typhimurium. Compared with free cephalothin, following intravenous administration, liposome-encapsulated cephalothin was cleared from the circulation more rapidly and concentrated in the liver and spleen. Treatment of infected mice with the liposome antibiotic complex was more efficacious in terms of reducing the number of S. typhimurium in these organs as compared with the free antibiotic. The results suggest that liposome-encapsulated antimicrobial agents may possess a therapeutic advantage in the treatment of diseases caused by facultative intracellular bacteria since this manipulation favors delivery of the entrapped antibiotic to intracellular sites occupied by S. typhimurium.

The effect of opsonic antibody on resistance of susceptibility of three strains of mice, C57Bl/10, BALB/c, and CBA to the intracellular bacteria Listeria monocytogenes, Salmonella typhimurium, and Brucella abortus was tested. Bacteria were opsonized by serum treatment before their injection into mice, or the mice were preimmunized by injection with alcohol killed bacteria which induces antibody without macrophage activation. Antibody did not increase the rate of clearance of Listeria from the bloodstream, nor did it affect the subsequent growth of that organism in the spleen and liver. Blood clearance of S. typhimurium and of B. abortus was increased by preopsonization with specific antibody, indicating that opsonins were a limiting factor in resistance to these two bacteria. However, neither opsonization before infection nor immunization with alcohol killed vaccines had any effect on the strain distribution of resistance/susceptibility, which differs for each of the three intracellular pathogens. Thus, even in the presence of adequate opsonization the three strains of mice showed different patterns of resistance/susceptibility to Listeria, S. typhimurium, and B. abortus. This implies that each has a unique cellular mechanism of early nonspecific resistance.

In order to determine the correlation between the in vitro model of monocyte differentiation and its in vivo counterparts, cell surface phenotypes of monocytes in culture and mature tissue macrophages were analyzed using monoclonal antibodies, M1/70, TA-1 anti-HLA-DR, and a heteroantisera prepared to macrophage cell line U937. Following 7 days in culture the reactivity of monocytes with M1/70 diminished from 70 +/- 9% to 31 +/- 8%. Similarly, the reactivity to TA-1 dropped from 88 +/- 8% to 23 +/- 7% and for anti-DR, from 79 +/- 5% to 41 +/- 16%. Reactivity with anti-U937 remained unchanged. This altered phenotype of cultured monocytes was found to approximate that of resident splenic macrophages (MO). In addition, freshly isolated monocytes and peritoneal exudate MO (PEMO) were found to be functionally similar in their inability to phagocytize via the C receptors. These results suggest that PEMO arriving recently into the peritoneal cavity from peripheral blood may be midway in transition between monocytes and mature MO, and that the phenotype and functional changes attributed to monocytes in culture may reflect changes that occur in vivo in the transition to tissue MO.

The mobility of plasma membrane receptors for lectins concanavalin A (Con A), phytohemagglutinin (PHA), garden pea agglutinin (PSA), lentil agglutinin (LCA), peanut agglutinin (PNA), soybean agglutinin (SBA), wheat germ agglutinin (WGA), and perch spawn agglutinin (PFA), the presence of binding sites for sheep erythrocytes, the presence of Fc and complement receptors, as well as pinocytic and phagocytic activities were investigated in normal peritoneal macrophages from conventionally reared (CV) and germ-free (GF) rats. Differences varying according to the lectin used were found in lectin-receptor-complex lateral mobilities measured as a function of patch and cap formation. Germ-free-rat-derived macrophages showed a significant decrease in the average amount of SBA binding sites per cell as determined by 125I-SBA labeling. The percentage of complement- and Fc-receptor-bearing macrophages was lower in GF rats, in contrast to the higher percentage of macrophages forming spontaneous rosettes with sheep erythrocytes. The pinocytic activity as determined by the neutral red uptake assay exhibited a threefold increase in GF rat-derived macrophages in comparison to CV ones. On the other hand, phagocytosis was more intense in macrophages from conventional rats, as detected by the engulfing of CdCO3 microcrystals. Our results, together with other recent reports, indicate that the earlier opinion that the peritoneal macrophages of GF animals do not differ essentially from those of conventional ones needs to be revised.

The splenic plaque forming cell (PFC) response of mice to an intraperitoneal injection of sheep erythrocytes was severely depressed by prior treatment with Corynebacterium parvum given four days beforehand by the same route. However, total antibody levels were less affected, and soon attained near normal titres. This implied that the effects of C. parvum were limited to the spleen, and that other tissues gave a substantial response during the period when the splenic response was suppressed. Equally, this apparently local immunosuppressive effect of C. parvum failed to inhibit the eventual development of a normal memory cell pool. It was also shown that primed cells in the spleen, challenged during the period when C. parvum inhibited primary IgG responses, were relatively refractory to its suppressive effects.

Macrophage activity in relation to Marek's disease was investigated by determining phagocytic indices in vivo and by examining virus plaque-inhibiting activity of peritoneal macrophages in vitro. No correlation was observed between phagocytic index and resistance in different genetic strains of chickens. Infection with Marek's disease virus increased both phagocytic indices and the plaque-inhibiting activity of peritoneal macrophages, more so in susceptible than in resistant chickens. There was an association between increased macrophage activity and virus replication, and it is suggested that the enhancement of macrophage activity results from activation indirectly caused by the presence of Marek's disease virus or viral antigens.

An intraperitoneal injection of latex in rabbits was found to give rise to an increase in the number of macrophages at the site of inflammation and a concomitant monocytosis in the peripheral blood. The results showed that during the initial phase of the inflammatory reaction a humoral factor is present in the circulation of these animals that stimulates the monocyte production in the bone marrow in a concentration-dependent way. This factor has been called the factor increasing monocytopoiesis (FIM), in analogy with the name given to the factor previously found in mice. Rabbit FIM is cell-line specific since it has no effect on granulocyte or lymphocyte production, has an estimated molecular weight of between 10,000 and 25,000 daltons, was found to be sensitive to treatment with proteases, to be unaffected by glycosidases, and to be readily inactivated in vitro at 37 degrees C. Neither rabbit nor mouse FIM is species specific, since rabbit FIM evoked moderate monocytosis in mice and vice versa.