Dispersal, survivorship, and host selection of Culex erythrothorax (Diptera: Culicidae) associated with a constructed wetland in southern California.

Three mark-recapture studies were carried out at a constructed wetlands facility in San Jacinto, CA, to examine the dispersal and population ecology of the most abundant host-seeking mosquito, Culex erythrothorax Dyar, collected in carbon dioxide-baited traps. Recapture rates were 0.3, 7.4, and 13.9% for August, September, and October, respectively. The mean distance traveled per night was approximately 0.5 km, and females were not recaptured farther than 2 km from the release site. Most marked individuals (> or = 99.5%) were recaptured within 0.5 km of the release point. Marked individuals were recaptured for 33 d after release. Horizontal estimates of survival calculated using recapture data were 0.89, 0.87, and 0.84/d for August, September, and October, respectively. Temporal differences in the recapture rate were attributed to the effects of blood meal acquisition on host-seeking activity versus effects of mortality and strong developmental site fidelity on weekly recapture rates. Partially engorged females collected by CO2-baited traps at the wetland fed predominantly on cattle indicating that host-seeking females were using hosts at dairies surrounding the wetland and were returning to the wetland for resting before seeking an additional blood meal. Estimates of the gonotrophic cycle length and survivorship (vertical estimates) were problematical because of the low parity rates for females collected by CO2-baited traps. Limited dispersal and long survival of Cx. erythrothorax are important factors in the development of large populations at constructed wetlands.

Possible 110 kDa receptor for interleukin 2 in the chicken.

Chicken lymphoblasts were generated from spleen cells which had been incubated with concanavalin A (Con A) for 48 h. Monoclonal antibodies (mAbs) were produced by immunizing mice with 48-h Con A lymphoblasts. These antibodies were used to identify chicken lymphokine receptors on Con A-activated lymphocytes. The cellular enzyme immunoassay (EIA), with lymphoblasts and spleen cells as the target cells, was used to select for specific mAbs. One mAb was found by EIA to have a strong response against the lymphoblasts but weak against resting spleen cells. By immunofluorescence staining, it reacted strongly with lymphoblasts and weakly with resting spleen, erythrocytes, and bursal cells. This mAb was also shown to inhibit the lymphokine activity present in conditioned medium that was collected from 24-h cultures of Con A-activated spleen cells. By immunoprecipitation, this mAb precipitated a lymphoblast surface antigen with a molecular weight of about 110 kDa. This receptor may be analogous to the putative interleukin 2 gamma subunit recently described in human and mouse cell lines.

The western fence lizard Sceloporus occidentalis: evidence of field exposure to Borrelia burgdorferi in relation to infestation by Ixodes pacificus (Acari: Ixodidae).

The role of the Western fence lizard Sceloporus occidentalis in the enzootiology of the Lyme disease spirochete Borrelia burgdorferi was evaluated in the Hopland and Ukiah areas of Mendocino County, California. In 1989, half of 74 lizards collected monthly from April to October at Hopland were infested by the immature western black-legged tick Ixodes pacificus at a mean intensity of 6.0 ticks per lizard. The prevalence of infestation of lizards by immature I. pacificus (36 of 73) at Ukiah was similar, but the mean intensity (12.9) was approximately twice as great. Overall, zero of 223 larvae and 2 (0.6%) of 330 nymphs from both sites were found to contain spirochetes by direct immunofluorescence. Larval and nymphal I. pacificus fit the negative binomial distribution in spring, and the prevalence and abundance of these stages were significantly greater in spring than in summer at both sites. Spirochetes were not visualized in thick blood films prepared from 133 lizards from both localities. Plasma antibodies against B. burgdorferi were detected in seven of 10 experimentally inoculated lizards, in five (8%) of 63 lizards from Hopland, and in 10 (14%) of 70 lizards from Ukiah. Adult lizards had a significantly greater tick burden and seropositivity rate than juvenile lizards only at Ukiah. In 1991, efforts to detect and culture spirochetes from the blood of 21 wild-caught lizards and from the tissues of 189 associated ticks that fed xenodiagnostically on them were unsuccessful.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency of chicken CD4+ and CD8+ cells. Genetic control and effect of Rous sarcoma virus infection.

In chickens from congenic inbred lines CB and CC that differ only in the major histocompatibility complex (MHC), we observed significantly different percentages of CD4+ and CD8+ cells in peripheral blood lymphocytes (PBL) and spleen. Positive cells were detected by indirect immunofluorescence test as analysed by flow cytometry. In both PBL and spleen cell suspensions, the number of CD4+ cells was significantly higher in CB than in CC chickens, whereas in CC birds there was a higher percentage of CD8+ cells than in CB. These statistically significant differences were under the MHC control. We found no statistically significant influence of regressions or progression of Rous sarcoma virus-induced tumours on the percentage of peripheral T cells and on the interleukin-2 production in vitro.

Characterization of a receptor on activated chicken T cells.

Chicken lymphoblasts were generated from spleen cells which had been incubated with concanavalin A (Con A) for 48 h. Monoclonal antibodies were produced by immunizing mice with 48-h Con A lymphoblasts. The cellular ELISA, with lymphoblasts and spleen cells as the target cells, was used to select for specific monoclonal antibodies. A monoclonal antibody was found to have strong response against the lymphoblasts but not resting spleen cells. By immunofluorescence staining, this monoclonal antibody reacted strongly with lymphoblasts and did not react with resting spleen cells. This monoclonal antibody was also shown to inhibit the lymphokine activity present in conditioned medium (CM) which was collected from 24-h cultures of Con-A-activated spleen cells. In immunoprecipitation, this monoclonal antibody precipitated a lymphoblast surface antigen with a molecular weight of about 45 kDa.

Mosquito bionomics and the lack of arbovirus activity in the Chino area of San Bernardino County, California.

Mosquito bionomics, including temporal abundance, metabolic status, and blood-feeding patterns, and arbovirus activity were studied at representative dairy and residential habitats in Chino, Calif., during 1987 and 1988. Host-seeking Culex tarsalis Coquillett and Cx. quinquefasciatus Say females were more abundant and appeared earlier each season at traps near dairy breeding sources than at traps in residential areas, whereas Cx. stigmatosoma Dyar, which also breeds in dairy effluent, was most abundant at residential traps. All three Culex species remained gonotrophically active throughout winter and did not appear to enter diapause. Dairy cows diverted the normally ornithophagic Cx. tarsalis and Cx. quinquefasciatus females from avian hosts in dairy, but not in residential, habitats. Cx. stigmatosoma fed almost exclusively on birds. The diversion of host-seeking Cx. tarsalis females to bovine hosts and reduced abundance because of mosquito abatement may have combined to reduce the receptivity of the Chino area to St. Louis encephalitis virus.

Mosquito abundance and bionomics in residential communities in Orange and Los Angeles Counties, California.

Mosquito abundance and bionomics were studied intensively during summer and spring at two residential communities of contrasting economic status. Culex quinquefasciatus was the most abundant adult and immature mosquito collected in both communities, followed by Culiseta incidens, Culex stigmatosoma, and Culex tarsalis. Cx. stigmatosoma and Cx. tarsalis were more abundant in CO2 traps hung in tree canopy than at ground level and fed most frequently on birds. Cx. quinquefasciatus was abundant in both ground level and tree canopy CO2 traps and fed on both mammals and birds. Cs. incidens was collected most frequently by ground level CO2 traps and fed primarily on dogs. Cx. quinquefasciatus and Cs. incidens readily exploited peridomestic breeding sources, and resting adults were aggregated at houses with positive breeding sources. Although Cx. stigmatosoma and Cx. tarsalis larvae were collected primarily at peripheral breeding sources, the dispersion of resting adults was still clumped at houses within both communities. Mosquitoes were most abundant in the more affluent community due to an increased number of breeding sites created by automatic watering devices and poorly managed peripheral drainage channels. Resident opinion of recent mosquito annoyance was not related to the presence of mosquito breeding sources or the abundance of either resting or host-seeking mosquitoes.

Failure to alter neonatal transplantation tolerance by the injection of interleukin 2.

It has been postulated that the establishment of acquired, neonatal immunologic tolerance is due to a "deficit" in interleukin 2 (IL-2). To test this hypothesis, chickens were made immunologically tolerant to both major and minor histocompatibility antigens by transplantation of skin grafts onto newly hatched recipients. In this study, we injected various doses of IL-2 and concanavalin A simultaneously with transplantation and in some cases, several days posttransplantation, and we failed to enhance graft rejection. These results may have practical importance in respect to the clinical use of recombinant IL-2. Injection of IL-2 in and around surviving skin grafts also failed to alter skin graft survival.

Production in vitro of thyroglobulin autoantibody by obese strain (OS) chickens.

Thyroglobulin autoantibody (Tg-AAb) can be spontaneously produced in vitro with thyroid infiltrating lymphocytes (TIL) collected from Obese strain chickens 3.5 and 4 weeks old. Attempts to enhance Tg-AAb synthesis with two known polyclonal stimulators of immunoglobulin synthesis in chickens, Staphylococcus aureus Cowan strain 1 and dextran sulphate, failed to increase Tg-AAb production in vitro. Spleen cells and peripheral blood lymphocytes obtained from the same chickens as the TIL and older chickens known to produce moderate to high levels of Tg-AAb in vivo did not produce autoantibody either spontaneously or in the presence of polyclonal Ig stimulators with one exception. With this single, exceptional chicken we obtained a small amount of Tg-AAb produced in vitro with spleen cells. This suggests that in the OS chicken TIL, and to a much lesser extent, the spleen, contribute to the total Tg-AAb produced in this model of autoimmune thyroiditis.

Partial characterization of chicken spleen cell culture supernatants stimulated with Staphylococcus aureus.

The role of accessory cells in the proliferative response of chicken spleen cells to Staphylococcus aureus Cowan I (SAC) was examined. It was found that chicken spleen cells cultured with SAC produced a soluble molecule capable of causing proliferation when culture supernatants were added to spleen cells. The molecules responsible for this activity were stable in terms of exposure to extremes of heat and pH. Gel filtration of culture supernatants revealed biological activity, over a broad range of molecular weights, as measured by spleen cell proliferation. Similar findings were obtained when SAC was sonicated and evaluated following gel filtration. Exposure of culture supernatants to trypsin abrogated biological activity. The pivotal role of adherent cells in the generation of biologically active molecules is suggested by the ability of peritoneal exudate cells incubated with SAC to produce biologically active supernatants. In addition, the proliferative response of spleen cells to SAC was sensitive to chloroquine.

The role of soluble protein A in chicken spleen cell activation.

Soluble protein A (SpA) caused chicken spleen cell proliferation despite considerable evidence that SpA has no binding affinity for avian immunoglobulin (Ig). This biological activity was examined by several approaches. SpA-stimulated spleen cell cultures demonstrated no difference in proliferative responses regardless of the addition of human gamma globulin (HGG) or keyhole limpet hemocyanin. Adsorbents composed of HGG or hemoglobin were equally ineffective in abrogating the ability of SpA to induce spleen cell proliferation. In addition, ion exchange purified SpA was observed to induce comparable levels of spleen cell proliferation as ion exchange-affinity purified preparations. The lymphocyte subpopulation responsible for the observed proliferative response to SpA resides in the nylon wool adherent population. Nylon wool nonadherent lymphocytes failed to proliferate to SpA, but did proliferate in response to phytohemagglutinin as did nylon wool adherent cells. These data indicate that SpA is not responsible for the observed biological activity and suggest that components from Staphylococcus aureus other than SpA copurify during the preparation of SpA and are responsible for the activation of spleen cells.

B cell activation in chickens induced by Staphylococcus aureus.

Conventional mammalian polyclonal B cell activators were evaluated for activity in chicken spleen and peripheral blood lymphocyte (PBL) cultures. Although lipopolysaccharide was found to have a marginal influence on proliferation, two strains of the bacterium Staphylococcus aureus (Cowan I and Wood 46 strains) induced moderate proliferation in both spleen and PBL cultures. In spleen cell cultures the proliferating cell population was identified as the B cell. The mitogenic response required the presence of adherent cells since their removal eliminated the response. Evidence of in vitro polyclonal immunoglobulin synthesis could not be obtained. However, when administered intravenously, S. aureus induced polyclonal immunoglobulin synthesis.

Neonatal splenic suppressor cells in the chicken. I. In vivo suppression of the immune response to bovine serum albumin by normal and tolerized neonatal spleen cells.

The presence of active splenic suppressor cells in neonatal chickens, either normal or tolerant to bovine serum albumin (BSA), was examined by assessment of their effect on both primary and adoptively transferred secondary responses to BSA or sheep red blood cells (SRC). Both normal and BSA tolerized spleen cells were shown to be highly suppressive of secondary anti-BSA responses generated by specifically primed adult spleen cells in inert recipients. Suppression of the secondary anti-BSA response by normal spleen cells was slightly less effective than that seen with BSA tolerant spleen cells. Transfer of BSA tolerant spleen cells into normal recipients, followed by BSA challenge, prevented any significant primary anti-BSA response. In contrast, transfer of normal spleen cells into normal recipients, followed by BSA challenge, failed to show any suppression of the resulting primary response. Neither normal nor BSA tolerant neonatal spleen cells were capable of suppressing either primary or secondary responses to SRC. Thus, chickens tolerized to BSA have suppressor cells specific for the tolerizing antigen. We present evidence that both the tolerance associated suppressors and the suppressors detected in normal neonatal chickens are T cells.

Immunological tolerance in the chicken. III. Partial physiochemical characterization of two suppressive fractions from serum of chickens tolerant to bovine serum albumin.

Two soluble non-specific suppressive factors were isolated by gel chromatography from the serum of chickens tolerant to bovine serum albumin (BSA). Fraction I was found by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) to contain five proteins with mol. wts from 200,000 to 900,000 unreduced and six proteins that ranged from 70,000 to 180,000 when reduced. The composition was primarily protein, with a small amount of carbohydrate and lipid. One component was identified as IgM, one as a lipoprotein. The others remain unidentified. No evidence of the tolerogen, BSA, was found. The second factor, fraction III of both tolerant and normal serum, was found by SDS-PAGE to have two proteins with mol. wts of 54,000 and 78,000 in the unreduced form and contained a very small amount of protein, a large amount of carbohydrate, and no detectable lipid. Normal fraction III had two proteins with mol wts of 54,000 and 65,000 when reduced, whereas reduction did not affect tolerant fraction III. A soluble suppressive factor, secreted by cultured adherent cells of tolerant chickens, was found to be comparable to fraction III in molecular weight. Comparison of these results with those of other reported suppressive factors is made and possible identities of the suppressive components of fractions I and II are discussed.

Genetic polymorphism of a serum euglobulin of chickens which binds to antigen-antibody complexes.

Binding of a euglobulin from normal chicken serum to precipitating HSA anti-HSA complexes has been demonstrated. The binding appeared specific for the Fc-fragment of chicken antibody since it was not detected with rabbit Ag-Ab complexes. Two allelic allotypic markers of the euglobulin under genetic control from one locus (E-1) were found in chickens from two inbred strains. E-1 alleles segregated independently from those controlled by the B (major histocompatibility), M-1 and G-1 (Ig allotype) loci. Partially purified E-1 had a sedimentation coefficient of 15.6 S. and beta-globulin electrophoretic mobility.