IgE-mediated release of rat mast cell protease II, beta-hexosaminidase and leukotriene C4 from cultured bone marrow-derived rat mast cells.

Functional characteristics of cultured bone marrow-derived rat mast cells (BMMC) were studied. BMMC were shown to release in a time- and dose-dependent fashion the mucosal mast cell (MMC)-specific enzyme, rat mast cell protease II (RMCPII), following IgE-mediated activation in vitro. RMCPII release was temporally associated with that of the mast cell granule-derived enzyme, beta-hexosaminidase (beta-hex). Release of the pre-formed granule constituents, RMCPII and beta-hex, was associated with the generation of the membrane-derived lipid mediator, leukotriene C4 (LTC4) and, in older cultures, substantial amounts were generated (25.2 ng/10(6) BMMC). Absolute amounts of RMCPII, beta-hex and LTC4 released were dependent upon the age of the BMMC. These results extend our previous observations on the staining properties and protease content of rat BMMC and provide evidence that these cells are functionally, as well as histochemically, analogous to the MMC subset, which is so prominent during intestinal nematode infections in rats.     

Lack of L-selectin expression by cells transferring diabetes in NOD mice: insights into the mechanisms involved in diabetes prevention by Mel-14 antibody treatment

The process of mononuclear cell extravasation from the blood into the islets of Langerhans in nonobese diabetic (NOD) mice is dependent on the expression of a set of molecules, most of which remain to be defined. The observation that vascular addressins are expressed in inflamed islets raises the issue of the involvement of one of their ligands, L-selectin, in the pathogenesis of autoimmune diabetes. Treatment of NOD females with Mel-14, an antibody specific for L-selectin, reduced the spontaneous development of both insulitis and diabetes. Pretreatment of diabetic donors with Mel-14 decreased the capacity of their splenocytes to transfer the disease. However, the treatment of recipients had no effect on the transfer of diabetes by untreated diabetogenic splenocytes. To reconcile these apparently conflicting results, we fractionated spleen T cells from diabetic mice according to L-selectin expression. Diabetogenic cells were found only in the L-selectin subpopulation. Thus, diabetogenic cells in adult mice share phenotypic characteristics with activated/memory cells, and enter the pancreas using L-selectin-independent migratory pathways.     

Activation of rat complement by soluble and insoluble rat IgA immune complexes

The ability of rat monoclonal IgA, specific for 2,4-dinitrophenyl (DNA), to activate the complement (C) system of the rat was investigated using aggregated IgA or IgA immune complexes (IC). IgA was coated onto a solid phase, and tested for its capacity to bind C3 upon incubation at 37 degrees C in normal rat serum (NRS) in the presence of Mg-EGTA. Binding of C3 was observed dependent on the dose of dimeric (d-), polymeric (p-) and secretory IgA tested. In contrast, little C3 fixation was observed in this system with monomeric (m-) rat IgA or with mouse m- and d-IgA (MOPC315). Soluble and insoluble rat IgA IC were prepared using dinitrophenylated rat serum albumin (DNP8RSA) as antigen (Ag), and assessed for C activation. It was shown that insoluble IC (immune precipitates; IP) containing m-, d- or pIgA of rat origin activate the alternative pathway of rat C, as demonstrated by their capacity to induce C consumption in NRS in the presence of Mg-EGTA. When p- and m-IgA IP were compared for their capacity to activate C, it was found that p-IgA activated C four times as efficiently as m-IgA IP (at 2 mg/ml). Soluble rat IgA IC were prepared in an excess of DNP8RSA, fractionated by gel filtration on Sepharose 6B, and analyzed for C activation and antibody (Ab)/Ag ratio. In contrast to m-IgA IP, soluble m-IgA did not activate C. On the other hand soluble d-IgA IC activated C dependent on their concentration and size: at a concentration of 0.1 mg/ml high-molecular weight d-IgA IC with a high Ab/Ag ratio were four times as efficient as low-molecular weight IC with a low Ab/Ag ratio, and twice as efficient as IP prepared at equivalence. To demonstrate the induction by IgA of the assembly of the terminal membrane attack complex, trinitrophenyl (TNP)-conjugated rat red blood cells (TNP-RRBC) coated with d- or p-IgA were shown to be lysed in NRS in the presence of Mg-EGTA. No lysis of m-IgA-coated TNP-RRBC was observed. The results in this study demonstrate that both soluble and insoluble rat IgA IC activate the alternative pathway of homologous rat C. Alternative pathway activation by soluble rate IgA IC is dependent on the size of the IC. The degree of polymerization of the IgA Ab itself also influences C activation.     

Influence of adrenergic drugs on IgE production

The influence of some adrenergic drugs (fenoterol, salbutamol, terbutaline as stimulant; propranolol as blocker) on IgE production in the rat was investigated. The drugs were administered orally, mixed in the food. The stimulant drugs caused a significant decrease of total serum IgE but had no influence on the specific IgE antibody response. The beta adrenergic blocker caused a significant increase of total serum IgE but also had no influence on specific IgE. The effect of terbutaline was blocked by propranolol. No influence of these adrenergic drugs on IgA and IgM levels was observed.     

Anti-IgE and Con A-induced histamine release from mast cells of four rat strains: Correlation with total serum IgE

Anti-IgE- and Con A-induced histamine release from serosal mast cells were compared to each other and to total serum levels of IgE in non-immunized, alum-injected, and Silica gel-injected rats of the BN, Fischer, PVG, and SD strains. The results indicate that the degree of anti-IgE-and Con A-induced release is strain-dependent and varies with immunization conditions. Furthermore, there is a gross but not complete correlation between the degree of serosal mast cell histamine release induced by the two secretagogues. However, Con A- or anti-IgE-induced release could significantly be correlated to serum levels of total IgE only in the Fischer strain but not in the BN or the PVG strains. In the SD strain, Con A-induced release correlated to serum IgE levels in Silica gel-injected but not in alum-injected animals.Subsidiary of AB Astra, Sweden.     

Evidence that tissue mast cells derive from mononuclear phagocytes

A new method has been developed that allows in vitro differentiation of rat mast cells from precursor cells in the absence of feeder layers. In the present investigation, the precursor cells are further characterized as to their nature, state of activation and distribution in different organs of the rat. The data support our previously published evidence, based on morphology and enzyme-cytochemical reaction patterns that the precursor cells are mononuclear phagocytes. Peritoneal macrophages elicited by mineral oil, thioglycollate or proteose-peptone have lost the ability to differentiate into mast cells. Single cell suspensions of spleen and bone marrow contain mast cell precursors, while cells from mesenteric lymph nodes and thymus or purified lymphocytes never yield mast cells in this culture system.     

Interference of oral immunization with the intestinal absorption of heterologous albumin

Rats were immunized with human serum albumin (HSA) by a single intragastric administration of 200 mg of HSA. Two weeks later their capacity to absorb a similar intragastric test dose of HSA was found to be greatly impaired, the concentrations of HSA in mesenteric venous serum having been reduced to 33 %, 25 % and 60 % of those in similarly tested but unprimed animals, respectively 1, 2 and 3 hours after the intragastric test dose. Rats given antigen (HSA) together with intestinal secretions from intragastric immunized rats also showed a striking decrease in intestinal absorption of a test dose, compared to controls given the antigen together with nonimmune intestinal secretions. From these data it is concluded that local immunization of the gut impairs its capacity to absorb the corresponding antigen, and that this effect is largely due to the failure to absorb antigen bound to secretory antibodies.     

An improved screening system for the early detection of congenital dislocation of the hip

A screening programme for congenital dislocation of the hip in which physiotherapists examine all neonates is described, together with the results over a 7-year period. All easily reducible dislocated and dislocatable hips are splinted within 2-5 days of birth. Subluxable or "slidey" hips are identified and followed up but not splinted. Risk groups are also identified and followed up. There was a progressive decrease in the number of late diagnosed cases, a result suggesting that even late-presenting acetabular dysplasia can be eliminated by neonatal screening.