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R Blackstock

Publications and source records attributed to R Blackstock.

At least 19 recordsLinked to original sources
PubMed2000

Regulation of cytokine expression in mice immunized with cryptococcal polysaccharide, a glucuronoxylomannan (GXM), associated with peritoneal antigen-presenting cells (APC): requirements for GXM, APC activation, and interleukin-12.

Mice immunized with peritoneal exudate cells (PEC; used as antigen-presenting cells [APC]) that are pulsed ex vivo with cryptococcal capsular polysaccharide, a glucuronoxylomannan (GXM), exhibit increased survival times and delayed-type hypersensitivity reactions when they are infected with Cryptococcus neoformans. These responses are GXM specific. The present study revealed that GXM-APC immunization enhanced development of anticryptococcal type-1 cytokine responses (interleukin-2 [IL-2] and gamma interferon) in mice infected with C. neoformans. The enhancement was not GXM specific, because immunization with GXM-APC and immunization with APC alone had similar effects. GXM-APC (or APC) immunization caused small increases in the expression of type-2 cytokines (IL-4 and IL-5), but the increases were not always statistically significant. IL-10 levels were not regulated by immunization with GXM-APC or APC. GXM-APC prepared with PEC harvested from mice injected with complete Freund's adjuvant (CFA) enhanced type-1 cytokine responses, while GXM-APC prepared with PEC induced with incomplete Freund's adjuvant were ineffective. The CFA-induced PEC had an activated phenotype characterized by increased numbers of F4/80(+) cells that expressed CD40, B7-1, and B7-2 on their membranes. The immunomodulatory activity of the CFA-induced APC population was not attributed to their production of IL-12 because GXM-APC prepared with peritoneal cells harvested from IL-12 knockout mice or their wild-type counterparts were equally effective in augmenting the type-1 response. Blocking of IL-12 in the recipients of GXM-APC early after APC infusion revealed that early induction of IL-12 secretion was not responsible for the immunomodulatory response elicited by GXM-APC. These data, considered together with previously reported data, reveal that the protective activity of GXM-APC immunization involves both antigen-specific and nonspecific activities of GXM-APC.

Animals↗
PubMed1999

Pathogenesis of Cryptococcus neoformans is associated with quantitative differences in multiple virulence factors.

Two isolates of Cryptococcus neoformans were previously described as being highly divergent in their level of capsule synthesis in vivo and in their virulence for mice. The highly virulent isolate (NU-2) produced more capsule than a weakly virulent isolate (184A) in vitro under tissue culture conditions and in vivo. This investigation was done to determine if there were differences between the two isolates in other factors that might also contribute to virulence. Growth rate was not a factor as NU-2 grew more slowly than 184A. Based on PCR fingerprinting the two isolates were genetically different providing an opportunity to examine differences in multiple virulence traits. Quantitative analysis revealed that NU-2 expressed significantly more melanin and mannitol than did 184A. Although the isolates expressed the same capsular chemotype, NU-2 produced an additional structure reporter group (SRG) under tissue culture conditions that was not present when grown in glucose salts/urea/basal medium (GSU). Capsular polysaccharide SRGs of 184A were unaffected by shifting the growth conditions from GSU to tissue culture conditions. Our results suggest that pathogenesis of a C. neoformans strain is dictated by the quantitative expression of the strain's combined virulence traits. Regulators of the expression of these genes may be playing key roles in virulence.

Chromatography, Gas↗
PubMed1999

Differential regulation of immune responses by highly and weakly virulent Cryptococcus neoformans isolates.

Early inflammatory responses, delayed-type hypersensitivity (DTH) responses, and cytokine profiles were studied in mice infected by the pulmonary route with either a highly virulent isolate (NU-2) or a weakly virulent isolate (184A) of Cryptococcus neoformans. After infection, NU-2 remained in the lungs and the capsule became more pronounced during the first 24 h, whereas 184A induced an immediate inflammatory reaction and was rapidly cleared from the lungs. Cryptococcal antigen (GXM) appeared in sera early after infection with NU-2 and increased over the entire observation period. There was no detectable GXM in sera from 184A-infected mice. Both C. neoformans isolates induced anticryptococcal cell-mediated immune responses, but the responses had different profiles. DTH in NU-2-infected mice appeared at day 15 after infection and waned by day 21, whereas DTH in 184A-infected mice was present by day 5 and continued to increase. T helper 1 (Th1) cytokines (interleukin 2 [IL-2] and gamma interferon) were made by spleen cells early after infection with either isolate. NU-2-infected mice lost their ability to produce these cytokines, but 184A-infected mice retained it. IL-4, a Th2 cytokine, was not detected in infected mice. The regulatory cytokine IL-10 was made by spleen cells early but not later after infection with the highly virulent isolate and was not produced by spleen cells from 184A-infected mice. IL-10-deficient mice survived an NU-2 infection significantly longer than wild-type mice, suggesting that IL-10 is important in down-regulating the protective immune response. The induction of anergy appears to be responsible for the inability of NU-2-infected mice to control a C. neoformans infection.

Acute-Phase Reaction↗
PubMed1998

Liposomes, a potential immunoadjuvant and carrier for a cryptococcal vaccine.

Mice immunized with a cryptococcal culture filtrate antigen (CneF) emulsified in complete Freund's adjuvant (CFA) develop an anticryptococcal cell-mediated immune response (CMI). CMI is detected by delayed-type hypersensitivity (DTH) reactions and by enhanced clearance of Cryptococcus neoformans from infected tissues. The objective of this research was to evaluate anticryptococcal DTH reactivity and clearance of cryptococci from groups of mice immunized with CneF encapsulated into liposomes (CneF-liposome) and compare the results to results from mice immunized with CneF-CFA. CBA/J mice were injected subcutaneously with vaccines or control formulations (saline-liposome or saline-CFA). Six days later the mice were footpad tested to assess their DTH response to CneF or the animals were challenged intravenously with 10(5) viable C. neoformans to determine clearance of infection. Clearance was evaluated 7 days later by enumeration of cryptococcal colony forming units (CFU) in lungs, spleens, livers, and brains of the infected mice. The CneF-liposome formulation induced a positive anticryptococcal DTH response and elicited increased clearance of C. neoformans from tissues as compared to mice treated with saline-liposome. Even though the CneF-liposome preparation did not induce as strong of a DTH response or as much protection as did CneF-CFA, our results indicate that liposomes are promising carriers for immunization with cryptococcal antigen and that such immunization can provide some protection to subsequent infection with C. neoformans.

Adjuvants, Immunologic↗
PubMed1997

Presentation of cryptococcal capsular polysaccharide (GXM) on activated antigen-presenting cells inhibits the T-suppressor response and enhances delayed-type hypersensitivity and survival.

A hallmark of infection with Cryptococcus neoformans is depression of the immune system characterized by poor inflammatory responses and loss of delayed-type hypersensitivity (DTH) and antibody responses. T-suppressor cell (Ts) responses, elicited by the capsular polysaccharide (GXM) of the organism, are known to develop during infection. This study was undertaken to develop a method to inhibit the anti-GXM Ts response and thereby study the influence of the Ts response on immune responsiveness and survival in cryptococcosis. Antigen-presenting cells (APC), elicited with complete Freund's adjuvant (CFA), were treated in vitro with GXM (GXM-APC). The GXM-APC were injected intravenously into normal mice. These mice were resistant to induction of anti-GXM Ts cells when soluble GXM was administered in tolerogenic doses or when animals were infected with C. neoformans. Inhibition of the anti-GXM Ts response was specific to GXM as levan-APC did not inhibit induction of anti-GXM Ts cells. Inhibition of the anti-GXM Ts response could not be attributed to increased clearance of GXM due to induction of anti-GXM antibodies or other mechanisms. Anti-cryptococcal DTH responses were lost in mice by the second week of infection. However, treatment with GXM-APC, but not levan-APC, allowed mice to maintain their DTH response. GXM-APC pretreatment enhanced survival of infected mice compared with mice pretreated with levan-APC. These results show that GXM-APC induces immune responses that inhibit the induction of Ts responses and enhances DTH responses in infected mice. These responses correlate with enhanced survival after cryptococcal infection.

Animals↗
PubMed1997

Secretion of the C3 component of complement by peritoneal cells cultured with encapsulated Cryptococcus neoformans.

Two isolates of Cryptococcus neoformans were identified as being widely divergent in pathogenic potential after intratracheal infection of mice. These isolates differed in their ability to upregulate capsule synthesis when grown under tissue culture conditions, and this property correlated with virulence. We postulated that differential capsule synthesis may cause differential stimulation of macrophages to produce products such as complement components. To test this hypothesis, heat-killed yeast cells were incubated with normal mouse peritoneal cells (PC) before the level of C3 secreted was determined. Cryptococcal stimulants were grown on mycological agar, which does not promote capsule synthesis, or in RPMI 1640 at 37 degrees C in an atmosphere of 5% CO2, which stimulates capsule synthesis, to determine the role that the capsule plays in the induction of C3 secretion. C3 levels were elevated in cultures containing cryptococci grown in RPMI 1640 at 37 degrees C in an atmosphere of 5% CO2, and the level of C3 detected was correlated with the amount of capsule expressed by the yeast cell stimulant. Nonencapsulated mutants of C. neoformans did not stimulate C3 secretion. Purified capsular polysaccharide (glucuronoxylomannan [GXM]) also stimulated the PC to secrete C3. Two signals were required before GXM stimulated C3 secretion. The second signal was identified as endotoxin present in small amounts (0.06 ng per ml) in tissue medium. Endotoxin may provide a priming stimulus for PC to express receptors or other cytokines needed for effective stimulation of C3. These experiments show that enhancement of C3 secretion by C. neoformans is due to GXM and is correlated with the virulence of the cryptococcal isolate.

Animals↗
PubMed1991

Functional equivalence of cryptococcal and haptene-specific T suppressor factor (TsF). I. Picryl and oxazolone-specific TsF, which inhibit transfer of contact sensitivity, also inhibit phagocytosis by a subset of macrophages.

Monoclonal and conventional cryptococcal-specific T suppressor factors (TsF) (also called TsFmp) depress phagocytosis by a subset of macrophages, while picryl- and oxazolone-specific TsF depress the passive transfer of contact sensitivity. This paper shows that these haptene-specific TsF also inhibit phagocytosis by a subset of macrophages and, using this assay, that the anti-haptene TsF resemble the anti-cryptococcal TsF in five respects: (i) the need for reexposure to specific antigen to trigger the release of TsF; (ii) genetic restriction in action; (iii) possession of an antigen-binding site; (iv) expression of I-J determinants; and (v) inactivation by reduction and alkylation. Purification of the anti-picryl TsF by sequential affinity chromatography indicates that the inhibition of phagocytosis is due to the TsF itself and not to a TsF-antigen complex. The TsF inhibits phagocytosis by a direct action as macrophages treated with TsF and exposed to antigen do not release a second factor which inhibits phagocytosis. These results and those of the accompanying paper indicate that the anti-cryptococcal and anti-haptene TsF are functionally equivalent, antigen-specific suppressor factors.

Alkylation↗
PubMed1991

Functional equivalence of cryptococcal and haptene-specific T suppressor factor (TsF). II. Monoclonal anti-cryptococcal TsF inhibits both phagocytosis by a subset of macrophages and transfer of contact sensitivity.

Monoclonal anti-cryptococcal TsF (which inhibits phagocytosis by macrophages) and anti-picryl TsF use the same two circuits to block the transfer of contact sensitivity (CS). Both arm macrophages which then release a macrophage suppressor factor (MSF) when exposed to antigen. This MSF depresses the transfer of CS. The evidence suggests that a single molecular species of TsF (MW ca. 70 kDa), which bears an antigen-binding site and I-J determinant, is responsible for MSF production and inhibition of phagocytosis. Anti-cryptococcal TsF also arms the T acceptor cell which then releases nsTsF-1 after triggering with a specific antigen (SCPA). This nsTsF-1, which depresses the transfer of contact sensitivity, was authentic, as shown by its I-J positivity (in contrast to MSF) and its role in the production of nsTsF-2. As anti-picryl TsF also inhibits phagocytosis, it was concluded that anti-cryptococcal TsF, originally detected by the inhibition of phagocytosis, and anti-picryl TsF, originally detected by inhibition of CS, are functionally equivalent.

Animals↗
PubMed1989

Characterization of the macrophage subset affected and its response to a T suppressor factor (TsFmp) found in cryptococcosis.

Previous reports from our laboratory described the detection of a suppressor factor which inhibited the phagocytic activity of a macrophage subset in murine cryptococcosis and in classical models of immune tolerance. The suppressor factor was originally named PIL (phagocytosis-inhibiting lymphokine) but has recently been renamed TsFmp (T suppressor factor for macrophage phagocytosis) because it was found to resemble the antigen-specific I-J-restricted suppressor factors described by others. The current investigation revealed that TsFmp acted rapidly upon the macrophage (15 min or less) to exert its effect of inhibiting the phagocytic process. The time for the macrophage to recover from the effects of TsFmp was likewise very rapid. The ability of TsFmp to inhibit phagocytosis was limited to engulfment of particles by Fc and mannan receptors and did not extent to phagocytosis via complement receptors or by nonspecific mechanisms. The macrophage subset that responded to TsFmp was determined to be in the I-A+ and I-J-IM+ subset.

Animals↗
PubMed1989

Characterization of a suppressor factor that regulates phagocytosis by macrophages in murine cryptococcosis.

A T-suppressor factor which inhibits the phagocytic activity of a macrophage subset has been further characterized. This suppressor factor was first described for a murine model of cryptococcosis but was later found to be common to models of immunologic unresponsiveness. The suppressor factor was produced when suppressor cells were cultured in the presence of specific cryptococcal antigen. It could not be extracted from spleen cells and was not induced by antigen in cultures of lymph node cells. The suppressor factor was filtered through Amicon filters of 100-kilodalton (kDa) exclusion limit but was retained by filters excluding molecules of less than 50 kDa. By Sephadex G-100 chromatography, the factor eluted just ahead of bovine serum albumin (68 kDa). The activity of the suppressor factor could not be inhibited by anticryptococcal antibody, but it was inhibited by anti-I-J alloantiserum of the same genotype as the lymphocyte which produced the factor. Absorption with an encapsulated strain of Cryptococcus neoformans removed the suppressor factor from culture supernatants, while absorption with a nonencapsulated mutant or an unrelated yeast cell had not effect. On the basis of these observations, it was apparent that the suppressor factor was idiotypic in nature and that I-J and/or the I-J-interactive molecule played a role in the function of the suppressor factor. The requirement for antigenic stimulation for the production of suppressor factor in vitro distinguished it from the T-suppressor factor 3 described by others which regulates delayed-type hypersensitivity in cryptococcosis.

Absorption↗
PubMed1988

Inhibition of macrophage phagocytosis in cryptococcosis: phenotypic analysis of the suppressor cell.

Our laboratory has previously reported a suppressor cell mechanism to occur late in the course of a lethal infection with Cryptococcus neoformans. A soluble factor was found to be responsible for inhibition of the phagocytic activity of a subpopulation of peritoneal macrophages. The suppressor cell was identified as a T cell which required in vitro stimulation with specific antigen before the phagocytosis-inhibiting lymphokine (PIL) was produced. PIL action was allospecific and occurred in animals given tolerogenic doses of cryptococcal and noncryptococcal antigens. The current investigation has further characterized the T lymphocyte responsible for PIL activity. The suppressor cell was found to be in a cyclophosphamide-sensitive pathway. PIL activity was not detected when spleen cell populations were treated with anti-I-J and complement or anti-Lyt-2 and complement. Likewise, a mixture of anti-I-J-treated and anti-Lyt-2-treated cells was incapable of synthesizing the lymphokine. Treatment of spleen cells with anti-Lyt-1.2 or anti-L3T4 and complement did not eliminate PIL synthesis. Further analysis of the genetic restrictions associated with the PIL-macrophage interaction revealed regulation by the I-J subregion of the major histocompatibility complex.

Animals↗
PubMed1987

Induction of a macrophage-suppressive lymphokine by soluble cryptococcal antigens and its association with models of immunologic tolerance.

Soluble extracts of Cryptococcus neoformans were examined for their ability to induce a macrophage-regulatory T-suppressor cell known to appear in the spleens of mice infected with cryptococci. Suppressor cells were induced by injection of extracts of encapsulated or thinly encapsulated strains of cryptococci. Dose-response analysis showed that as little as 25 micrograms of soluble capsular polysaccharide antigen could induce significant suppressor cell activity, with maximum suppression occurring at a dose of 100 micrograms. The suppressor cells appeared within 1 week of injection of antigen and persisted for at least 2 months. Suppressor cells were induced in animals given tolerogenic doses of levan, human gamma globulin, and soluble capsular polysaccharide antigen. When these same antigens were administered in immunogenic form, no suppressor cell activity was detected. Therefore, the suppressive mechanism was common to models of immunologic tolerance and was not unique to cryptococcal disease or cryptococcal capsular polysaccharide antigen. The phagocytosis-inhibiting lymphokine produced by the suppressor cell population completely inhibited the phagocytic activity of only a portion of peritoneal exudate cells. Other macrophages in the population were not totally inhibited but exhibited a reduction in the number of yeast cells engulfed.

Animals↗
PubMed1985

An analysis of the presence of Fc receptors on bone marrow lymphoblasts in acute lymphoblastic leukemia. A Pediatric Oncology Group study.

The presence or absence of the Fc receptor (FcR) on bone marrow lymphoblasts was evaluated in 279 cases of acute lymphoblastic leukemia (ALL) by member institutions of the Pediatric Oncology Group (POG). The case material was classified as follows: 19 cases of positive (greater than or equal to 20% +), 24 additional cases as intermediate (greater than or equal to 10% but less than 20%), and the remaining 236 cases as negative (less than 10%). Intermediate and positive cases were relatively equally distributed between null cell leukemia and pre-B-cell leukemia, and there were one intermediate and two positive T-cell cases. One of two cases of B-cell leukemia was also positive. There were no distinguishing clinical or laboratory characteristics which distinguished the FcR+ cases, nor was the FcR of prognostic significance within ALL as a group or within immunologically defined phenotypes.

Adult↗
PubMed1985

Diphenylhydantoin-induced hypersensitivity reaction with interstitial nephritis.

A 10-year-old black girl had an episode of diphenylhydantoin(DPH)-induced exfoliative dermatitis, lymphadenopathy, hepatitis, peripheral eosinophilia, and transient renal failure. The findings of specific lymphocyte sensitization of DPH, a clinically typical delayed hypersensitivity reaction, multinucleated histiocytes in the renal interstitium, and negative renal immunofluorescence studies for immune reactants indicate that the child's renal injury was at least partially cell-mediated.

Autoantigens↗
PubMed1984

Non-specific immunosuppression by Cryptococcus neoformans infection.

Cryptococcus neoformans-infected animals were found to be immunosuppressed when tested by a variety of assays for immune competence. Primary humoral immune responses and delayed-type hypersensitivity reactions to sheep erythrocytes were suppressed in animals which had been infected for two weeks. Lymphocyte proliferation (LP) assays to sRBC stroma were also significantly diminished at two weeks of infection. Spleen cells of infected mice suppressed the LP response of sRBC immunized, normal mice in vitro. At least a part of the suppression could be attributed to a nylon wool non-adherent cell. Suppressor cells continued to be present in spleen cell suspensions following treatment with anti-T cell serum or anti-immunoglobulin and complement. When infected spleen cells were separated by adherence to plastic, both the adherent and non-adherent fractions exhibited suppressive activity. Incubation of infected spleen cells in tissue culture for 48 hr resulted in the elaboration of soluble immunosuppressive factors into the tissue culture medium. These data indicated that immune suppression in cryptococcosis can occur as a result of infection with Cryptococcus neoformans, and that at least one mechanism involved is the induction of adherent and non-adherent suppressor cells in the spleens of infected mice.

Animals↗
PubMed1984

Functional testing and chemical composition of cryptococcal extracts.

Three antigens were compared for their ability to detect immune responses in C57Bl/6 mice sensitized to Cryptococcus neoformans. Elicitation of responses in vitro was greatest with a urea extract antigen, followed in efficiency by an alkali extract and a soluble capsular polysaccharide preparation. The reactivity paralleled the protein content of the preparation.

Animals↗
PubMed1983

Chronic blepharitis and pyoderma of the scalp: an immune deficiency state in a father and son with hypercupremia and decreased intracellular killing.

An immune deficiency state is proposed as the cause of a disorder affecting a father and son with chronic dermatitis, purulent blepharitis with corneal ulceration, and scarring pyodermatous alopecia of the scalp. The results of immunologic investigation revealed abnormal neutrophil function with a variable decrease in intracellular killing, decreased lymphocyte transformation, increased serum IgG and IgE, and elevated serum copper levels. These findings will be compared with previously described immune deficiency disorders.

Adult↗