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Biomedical subjects

R M Welsh

Publications and source records attributed to R M Welsh.

At least 127 records · Page 7Linked to original sources
PubMed1981

Correlation of glycosphingolipids and sialic acid in YAC-1 lymphoma variants with their sensitivity to natural killer-cell-mediated lysis.

Sialoglycoconjugates and glycosphingolipids were quantitated in a series of variants derived from the YAC-1 lymphoma, known to be highly sensitive to natural killer (NK)-cell-mediated lysis. The variants, which had widely diverging sensitivities to NK cells, were obtained by a number of methods, including selection in the presence of NK cells, antibody to H-2, or antibody to the murine leukemia-virus-induced antigen, and by fusion of sensitive cells with an NK-resistant cell line, A9HT. The sensitivities of these cells to NK-cell-mediated lysis did not correlate with their sensitivities to anti-H-2a cytotoxic T cells. While no correlation could be made between the NK-sensitivity of these variants and their total cellular sialic acid, a statistically significant inverse correlation was observed between the levels of percentage neuraminidase releasable surface sialic acid of total labelled sialyl components and sensitivity to NK cells. This correlation with cell surface sialic acid was observed with either endogenous or lymphocytic choriomeningitis virus-induced activated NK cells as effectors. Neuraminidase treatment of insensitive target cells caused a moderate increase in sensitivity but failed to render the resistant targets as sensitive as YAC-1. Analysis of glycosphingolipids among the variants revealed a strong positive correlation between the total cell neutral glycolipid with chromatographic migration of asialo-GM2 and sensitivity to endogenous or activated NK-cell-mediated lysis. Significant correlations were not found with any other neutral glycolipids. However, ganglioside homologues with chromatographic mobility of GM1, GD1a, GD1b, And GT also showed a positive correlation with both endogenous and activated NK-cell-mediated lysis. The ratio of asialo-GM2 to GM2 had a highly significant positive correlation with sensitivity. These correlative results suggest that asialo-GM2 and certain gangliosides could be involved in binding or lytic events in NK cell:target cell interactions, and that high levels of sialic acid and sialylation on the surface may inhibit and/or modify such interactions. Further studies with these YAC variants should be useful for examining the biochemical bases of target cell-effector cell interactions in the NK-system.

Animals↗
PubMed1981

Metabolic inhibitors render "resistant" target cells sensitive to natural killer cell-mediated lysis.

L-929 cells were lysed by activated but not by endogenous natural killer (NK) cells, as reported previously. Nevertheless, L-929 cells bound to endogenous NK cells, as shown by target binding cell, cold target competition, and monolayer absorption assays. Treatment of L-929 cells with actinomycin-D or cycloheximide rendered them sensitive to lysis by endogenous NK cells and markedly increased their sensitivity to lysis by activated NK cells. Treatment with these drugs under the prescribed conditions did not affect the binding of L-929 cells to NK cells. Since others have shown that treatment with these drugs inhibits membrane repair processes and renders cells more sensitive to complement-mediated lysis, we hypothesize that membrane repair may be an important factor influencing a cell sensitivity to NK cells. This may be more important than NK-binding ability, since most cells can be lysed by (and therefore bind to) activated NK cells.

Animals↗
PubMed1980

Killing of normal cells by activated mouse natural killer cells: evidence for two patterns of genetic regulation of lysis.

Normal primary mouse thymocytes and peritoneal cells are sensitive for lysis by mouse spleen cells activated by in vivo infection with lymphocytic choriomeningitis virus (LCMV). With both thymocytes and peritoneal cells as targets, the active killer cell seemed to be an NK cell, as judged by high activity in the mouse mutant nude and low activity in the mouse mutant beige. Thymocytes from 1- to 3-week-old mice were found to be most NK-sensitive, while peritoneal cells showed highest sensitivity for lysis when harvested from older (6- to 8-week-old) animals. In a direct comparison the genetic regulation of NK activity against thymocytes and peritoneal cells was analyzed. The same strain origin of both target cells and effector cells in either system was used. With thymocytes as target cells, spleen cells from LCMV-infected C3H/St mice invariably showed the highest activity closely followed by cells from the BALB/c strain, while the SWR/J and the A/J strains both were considerably less reactive. The same pattern of high- or low-reactive strains was seen regardless of the genotype of the thymocyte target donor, and the same pattern of cytotoxicity was also seen against the YAC-I lymphoma target. An entirely different genetic regulation was active in the lysis of peritoneal cells, where a unique pattern of reactivity was seen for each effector cell genotype, dependent on the strain origin of the peritoneal target cell. In line with previous findings, syngeneic combinations of effector-target cells yielded little or no reactivity, while various allogeneic combinations showed considerable levels of activity. Also, primary cultures of embryonic fibroblasts were used as target cells. The genetics of the fibroblast target system was more similar to that seen in the thymocyte-YAC-I assay since no evidence for a preferential killing of allogeneic target cells was seen.

Animals↗
PubMed1980

Restriction specificities, alloreactivity, and allotolerance expressed by T cells from nude mice reconstituted with H-2-compatible or -incompatible thymus grafts.

Congenitally thymusless nude mice that lacked functional T cells were reconstituted with H-2-compatible or -incompatible thymus grafts taken from either fetal, newborn, or adult mice and transplanted under the kidney capsule or subcutaneously. Transplantation with unirradiated fetal (15--17 d) or newborn thymus grafts reconstituted the nude mice as assessed by their subsequent generation of virus-specific cytotoxic T cells in vivo or alloreactive T cells in vitro. The restriction specificity of T cells from homozygous mice was exclusively for the nude host H-2, as shown by direct cytolysis or by cold target competitive inhibition assays. irrespective of whether nude mice were reconstituted with H-2-compatible, semiallogeneic, or H-2-incompatible, unirradiated newborn or fetal thymus grafts (in order of decreasing efficiency of reconstitution). The restriction specificity for the nonhost H-2 of the thymus could not be demonstrated even after primary or secondary sensitization in an infected appropriate F1 environment. These nude mice reconstituted with fetal or newborn grafts were tolerant to the H-2 of the thymus donors. Nude mice transplanted with irradiated adult thymus grafts were reconstituted functionally with syngeneic or semisyngeneic but not with allogeneic thymus grafts. In homozygous nu/nu irradiated heterozygous recipients of F1 thymus grafts, the restriction specificity for the nonhost thymic H-2 could not be elicited upon adoptive sensitization in irradiated and infected F1 heterozygote stimulator mice; in fact, these chimeras' lymphocytes were not tolerant to the nonhost H-2. The discrepancy between the restorative capacity of unirradiated vs. irradiated thymus grafts suggests that precursors of T cells in nude mice can acquire restriction specificity and immunocompetence independently of a conventional, functioning H-2-compatible thymus if exposed to an allogeneic fetal or a newborn thymus that contains functioning thymocytes of donor type but not if reconstituted with an irradiated adult allogeneic thymus.

Animals↗
PubMed1980

Natural killer cell response to lymphocytic choriomeningitis virus in beige mice.

Lymphocytic choriomeningitis virus (LCMV) induced low levels of natural killer (NK) cell acitivity in C57BL6 mutant beige (bg/bg) mice, which had previously been reported to have no cytotoxic NK cells. NK cell-mediated lysis by bg/bg splenocytes was observed against a cell line (YAC-1) very sensitive to NK cell cytotoxicity, but not appreciably against a less sensitive cell line (L-929). The bg/bg mutant mice with this very low NK cell activity and control strains of mice (by/+, C57BL6) with high NK cell activity synthesized comparable amounts of virus and interferon in the spleen, suggesting that NK cells may not play a significant role, but not appreciably against a less sensitive cell line (L-929). The bg/bg mutant mice with this very low NK cell activity and control strains of mice (by/+, C57BL6) with high NK cell activity synthesized comparable amounts of virus and interferon in the spleen, suggesting that NK cells may not play a significant role, but not appreciably against a less sensitive cell line (L-929). The bg/bg mutant mice with this very low NK cell activity and control strains of mice (by/+, C57BL6) with high NK cell activity synthesized comparable amounts of virus and interferon in the spleen, suggesting that NK cells may not play a significant role in curtailing viral synthesis before the advent of the specific immune response mechanisms.

Animals↗
PubMed1980

Cytotoxic cells induced during lymphocytic choriomeningitis virus infection of mice: natural killer cell activity in cultured spleen leukocytes concomitant with T-cell-dependent immune interferon production.

The characteristics and specificities of spleen and peritoneal cytotoxic cells generated during lymphocytic choriomeningitis virus (LCMV) infection of C3H/St mice were examined. Activated natural killer (NK) cell activity was identified in fresh leukocyte populations from the 2nd to 8th days postinfection, whereas virus-specific cytotoxic T-cell activity was detected from the 6th to 14th days. When leukocytes were cultured overnight at 37 degrees C before assay, T-cell activity was still observed, but nonspecific activated NK cell-like cytotoxicity was only detected on the 6th and to a lesser degree the 8th day postinfection. Overnight culture of leukocytes taken earlier in the infection eliminated their NK cell activity. Similar activities were seen with spleen cell, plastic-adherent peritoneal cell, and nonadherent peritoneal cell populations. The virus-specific cytotoxicity observed with adherent peritoneal cells was due to contamination with cytotoxic T cells, as shown by H-2-restricted cytotoxicity and sensitivity to anti-theta antibody and complement. The nonspecific cultured day 6 effector cell from either the spleen or peritoneum displayed killing specificities and other physical properties identical to those of activated NK cells, but had sensitivities to anti-theta antibody and complement intermediate between activated day 3 NK cells and cytotoxic T cells. Culture stable NK-like cells were not found in athymic nude mice, suggesting a T-cell-dependent mechanism. Whereas LCMV spleen homogenates contained 10-fold-higher levels of interferon at day 2 than at day 6 postinfection, substantially more (nearly 20-fold) interferon was made in cultures of day 6 cells than day 2 cells. Spleen interferon was predominantly type I, whereas the culture interferon was predominantly type II, as shown by acid lability studies. Significant levels of interferon were produced by nylon-wool-passed day 6 spleen cells, and virtually all interferon production was eliminated by treatment of either day 2 or day 6 cells with antibody to theta antigen and complement, suggesting that T cells produced the interferon in vitro. Furthermore, athymic nude mice had no culture-stable NK cells 6 days postinfection, and spleen cells from them failed to produce significant levels of interferon in vitro. Addition of interferon (type I, fibroblast) to cultured C3H spleen cells affect the already elevated levels of cytotoxicity in day 6 cultures, suggesting that the NK cells in the day 6 culture were already activated. Our results suggest that T cells responding to LCMV infection secrete interferon type II which causes the continued activation of NK cells in culture. The resulting population of activated NK cells therefore appears to be relatively stable in culture and to express more theta antigen because of this T-cell dependence. Although one could mistakenly or allospecific cytotoxic T cells or cytotoxic macrophages, more careful examination shows that they are most likely activated NK cells...

Animals↗
PubMed1980

A comparative analysis of the cell surface properties of activated vs endogenous mouse natural killer cells.

Mouse natural killer (NK) cells can be activated by interferon and by interferon inducers, such as viruses. In the present report we compared the cell surface properties of the nonactivated "endogenous" NK cells from normal mice with NK cells activated in vivo by acute infection with lymphocytic choriomeningitis virus (LCMV) or in vitro by interferon. Several striking differences were found: 1) in vivo LCMV-activated as well as in vitro interferon-activated NK cells were more adherent to nylon wool columns than the endogenous NK cells; 2) activated NK cells were more EA-monolayer adherent than endogenous NK cells; this adherence could be blocked by streptococcal A protein, indicating that activated NK cells expressed greater Fc receptor mediated adherence; 3) LCMV-activated NK cells that passed through nylon wool columns expressed relatively low EA adherence properties; 4) the sensitivity of NK cells to anti-theta serum + complement treatment was increased in spleen cells late after LCMV infection (day 6 to 7) but not in spleen cells early after infection (day 2 to 3); 5) as shown by centrifugal elutriation, LCMV-activated spleens contained a population of large NK cells that were not present among endogenous spleen cells. In contrast to previous reports, these findings show that there are several distinct changes as a result of both long-term in vivo activation or of short-term in vitro activation of NK cells. These changes might functionally be involved in the increased lytic ability of activated NK cells.

Animals↗
PubMed1978

Cytotoxic cells induced during lymphocytic choriomeningitis virus infection of mice. I. Characterization of natural killer cell induction.

Lymphocytic choriomeningitis virus (LCMV) infection of C3H/St, nude (BALB/c background), and other mice induced high levels of natural killer (NK) cell activity in the spleen and peritoneum. L-929 cells were used as targetsand were not lysed by spleen or peritoneal cells from uninfected mice. The cytotoxic cells were characterized as NK cells because they were nonadherent, nonphagocytic lymphocytes lacking theta and immunoglobulin antigens on their plasma membranes. Their activity was sensitive to 6 mM EDTA and to heating for 5 h at 37 degrees C, but resisted treatment with 0.5 percent trypsin. No role for antibody could be demonstrated in these assays. Relative to cytotoxic T-cell activity, the induction of NK cell activity was resistant to X-irradiation of mice with 1,000 rads but was sensitive if mice were first treated with Strontium-89, a bone-seeking isotope. NK cells were induced by LCMV in all tested strains of mice. In C3H/St mice NK cell activity was detected as early as 1 day and peaked at 3 days postinfection. Maximum activity in C3H/St mice was observed in mice 5-10 wk of age, but significant NK activity was also induced in newborns, which subsequently carried virus in their tissues for the duration of their lives. Older LCMV-carriers did not have detectable spleen NK cell activity. No memory oranamnestic response could be demonstrated for NK cell induction. NK cell activity was not induced by LCMV challenge of LCMV-immune mice, but was induced in those mice by infection with Pichinde virus, a closely related virus. The advent of NK cell activity correlated with the synthesis of interferon in LCMV-infected mice. Culture fluids lacking virus infectivity but containing interferon induced cytotoxic cell activity in nude and C3H/St mice. These experiments suggest that LCMV induced NK cells via an interferon-dependent mechanism. When studied in several strains of mice, the continued expression of NK cell activity did not seem to directly correlate with spleen interferon levels, suggesting that additional factors may play a role as well in maintaining the activity of the NK cell in vivo.

Animals↗
PubMed1978

Some ultrastructural effects of persistent infections by the rickettsia Coxiella burnetii in mouse L cells and green monkey kidney (Vero) cells.

Mouse fibroblasts (L-929) and Vero (green monkey kidney) cells were infected with the rickettsia Coxiella burnetti, and persistent infections developed and were studied over a 6- to 10-month period. Ultrastructural comparisons were made between the two infected cell types, and both were tested cytochemically for the presence of acid phosphatase, a marker enzyme of lysozymes. Rickettsiae were always observed within vacuoles, and some infected L cells showed flattened endoplasmic reticulum as compared with uninfected cells. Rickettsiae in Vero cells were most often seen in vacuoles containing whorls of membranes ("myelin configurations") which were also seen in uninfected cells. Rickettsiae in Vero cells were pleomorphic, with acid phosphatase reaction product in their periplasmic space. This suggests either rickettsial degradation by lysosomal enzymes which penetrated the cell envelope or a penetration after the rickettsiae were dead. Vacuoles of infected Vero cells showed much more reaction product than that in infected L cells, and most rickettsiae in L cells had a normal appearance and showed no reaction product in their periplasmic space.

Acid Phosphatase↗