phytohemagglutinin-P Research Articles

The Effects of Temperature and Oleic Acid on Murine Memory and Virgin T Cell Activation: Interleukin-2 Secretion and Interleukin-2 Receptor Expression

Previous studies established that low in vitro temperatures (27°C, termed nonpermissive) suppressed murine primary thymus-dependent (TD), but not primary thymus-independent (TI) or secondary TD, antibody responses. Suppression was rescued by the addition of oleic acid (18:1), recombinant interleukin (rIL)-2 and/or rIL-4, but not rIL-1, These observations suggested that low temperatures suppress the functions of virgin T cells (Tv) but not those of memory T cells (Tm), B cells, or accessory cells and that hypothetically 18:1 may rescue suppressed responses by altering the membranes of Tv cells, allowing them to proliferate and subsequently secrete interleukins. In this study negatively selected Tm and Tv cells were stimulated with various mitogens at 37 or 27°C. The results indicated that proliferation was suppressed at 27°C to all mitogens tested. The subsequent addition of 18:1 induced proliferative responses at 27°C to both concanavalin A (Con A) and a combination of 12-O-tetradecanoylphorbol 13-acetate (TPA) and calcium ionophore (A23187), but not to phytohemagglutinin-P (PHA). Both Tm and Tv cells showed significant secretion of IL-2 and expression of IL-2 receptor (IL-2R) at 27°C in response to all mitogens, irrespective of proliferation, and the subsequent addition of 18:1 caused little or no change in the levels of IL-2 secretion or IL-2R expression. These findings indicate that suppression of Tm and Tv cell proliferative responses occurs irrespective of IL-2R expression and, unlike antibody production, of IL-2 secretion. Furthermore, it appears that 18:1 can synergistically act with Con A or TPA/A23187, but not PHA, in activating Tm and Tv cells to induce proliferation at 27°C. These findings suggest differences in signal transduction mechanisms between these various mitogens.

The effects of corticosteroid hormones and thyroid hormones on lymphocyte viability and proliferation during development and metamorphosis of Xenopus laevis

Abstract Metamorphosis in the South African clawed frog, Xenopus laevis, is characterized by a striking loss of lymphocytes in the thymus, liver, and spleen. Changes in the proliferative responses of splenocytes and thymocytes to T cell mitogens and semi-allogeneic cells are also observed at metamorphosis. Because the levels of circulating thyroid hormones (TH) and corticosteroid hormones (CH) increase dramatically during the climax of metamorphosis, we have investigated the possible role of TH and CH as mediators of the changes in lymphocyte numbers or lymphocyte function. Here we report on the in vitro effects of CH and TH on lymphocyte viability and on phytohemagglutinin-P (PHA)-stimulated lymphocyte proliferation at prometamorphosis and climax of metamorphosis. We have observed consistently significant inhibition of proliferation by corticosterone. In contrast, we have observed inconsistent inhibition of proliferation by both thyroxine (T 4) and triiodothyronine (T 3). In short-term studies, the viability of thymocytes and splenocytes was reduced in the presence of CH but not TH. These observations are consistent with a hypothesis that loss of larval lymphocytes and changes of lymphocyte function at metamorphosis may be due to elevated concentrations of CH rather than TH. Because CH have been shown to enhance TH-induced effects during metamorphosis, we looked at the combined effects of these agents on PHA-stimulated lymphocyte proliferation. While each agent was inhibitory in several experiments, there was no significantly greater inhibition when splenic lymphocytes were cultured with both.

Effects of thyroid hormone deprivation on immunity in postmetamorphic frogs

Previously, we showed that sodium perchlorate treatment of larval frogs ( Xenopus laevis) interferes with the normal expansion of T and B lymphocytes and development of an adult-type T-cell population. It was unclear whether these effects resulted from preventing metamorphosis or from long-term thyroid hormone (TH) deprivation. To try to distinguish between these possibilities, we have now studied the effects of perchlorate treatment beginning immediately after metamorphosis. After 5 months, treated animals, but not untreated controls, had large thyroid goiters, were significantly smaller, and had significantly fewer erythrocytes, thymocytes, and splenocytes. Although the number of IgM − splenocytes and thymocytes was reduced, the estimated percent of major histocompatibility complex (MHC) class II + cells within this subset was not significantly different from that of controls. Furthermore, splenocytes from perchlorate-treated frogs could respond normally by [ 3H]TdR incorporation to the T-cell mitogens, phytohemagglutinin-P (PHA) and concanavalin A (Con A). Thus, unlike perchloratetreated larvae, perchlorate-treated juveniles appear to be able to develop T cells with an adult phenotype competent to respond to activation and proliferation signals.

Swine interleukin 2 activity produced by mesenteric lymph node cells.

Swine interleukin 2 (IL-2) activity was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay using murine IL-2 dependent cell line (CTLL-2). The culture supernatant of mesenteric lymph node (MLN) cells stimulated with phytohemagglutinin-P (PHA) induced a generation of MTT formazan in a dose-dependent manner, suggesting dose-dependent proliferation of CTLL-2. The maximal swine IL-2 activity was observed in the culture of MLN cells at 1 to 2 x 10(7) cells/ml when stimulated with 20 to 40 micrograms/ml PHA for 48 hr. Based on these findings, a large culture of MLN cells to prepare swine IL-2 were performed under the following condition; cell concentration of 1 x 10(7) cells/ml, PHA concentration of 20 micrograms/ml, a culture scale of 200 to 400 ml, and a stirring speed of 30 rpm. Swine IL-2 activity was detected from 4 hr after PHA stimulation, and rapidly increased until 16 hr. Almost maximal IL-2 activity in stirring culture was observed at the incubation of 20 hr. Swine IL-2 was partially purified by Sephacryl S-200 gel filtration and the estimated molecular weight was about 32 kD based on the peak of IL-2 activity. The pI value of swine IL-2 was estimated to be approximately pH 5.3. Swine IL-2 was sensitive to acid (pH 3.2) or alkaline (pH 10.5), 4 or 8 M urea, trypsin, and the heating at 70 degrees C. These physico-chemical properties of swine IL-2 was similar to those of human, murine or feline IL-2.

Characterization of dog interleukin-2 activity.

Proliferative activity of murine interleukin-2 (IL-2) dependent T cells (CTLL-2) was detected in the culture supernatant of canine peripheral blood lymphocytes (PBL) stimulated with phytohemagglutinin-P (PHA-P), and was defined as dog IL-2. The highest production of IL-2 was obtained under the conditions in which a PBL population of 2 x 10(6) cells/ml was stimulated with PHA-P at a concentration of 10 micrograms/ml at 38 degrees C for 48 hr. Dog IL-2 activity was significantly inhibited by heating at 65 degrees C, acidification under pH 4, alkalification over pH 10, and trypsin exposure. A peak of dog IL-2 activity was detected in the fraction with a molecular weight of approximately 31,000 by gel filtration. Long-term culture of canine lymphocytes was successful over 10 passages by using dog IL-2 with PHA-P-stimulation every 3 passages. The cultured cells mostly consisted of small- and medium-sized lymphocytes. These cells reacted to anti-dog thymocyte rabbit serum and anti-dog Thy-1 mouse monoclonal antibody. These cells were therefore considered to originate in T-lineage lymphocytes. Cytostasis of PBL from intact dogs reacting to canine transmissible venereal sarcoma cells was increased significantly when PBL was cultured for more than 30 days with homologous IL-2.

Augmentation of phorbol ester-induced T cell proliferation by agents which raise intracellular cyclic adenosine monophosphate

Although raising intracellular cyclic adenosine monophosphate (cAMP) levels is generally considered to be inhibitory on the mitogen-induced T cell proliferation, in this study we have shown that the addition of either dbcAMP (50 μ M) or cholera toxin (1 ng/ml) resulted in an increase in [ 3H]thymidine uptake in PBMC cultures stimulated with phorbol ester, 12-tetradecanoylphorbol 13-acetate (TPA), or with a combination of TPA plus anti-CD3 mAb (mAb 235). In contrast, under similar culture conditions, the phytohemagglutinin-P (PHA-P) response was inhibited by these agents as has been reported. The augmentative effect of dbcAMP in PBMC cultures was due to an increase in IL-2 production and not to increased in IL-2R-α chain expression. The enhancing effect of dbcAMP and CT observed with PBMC was monocyte dependent and not seen with purified T cell preparations. The addition of monocytes reconstituted the ability of intracellular cAMP elevating agents to augment the T cell response to TPA with and without mAb to CD3. The monocytes mediate their action via soluble factor(s) with molecular weight (m.w.) of more than 10 kDa. Neither rIL-1, rIL-6, nor rTNF-α have any augmentative effect as contrast with the supernatant from treated monocytes. Taken together, our results indicate that cAMP can play a positive regulatory role in T cell proliferation due to factor(s) secreted by dbcAMP-treated monocytes resulting in increased IL-2 synthesis in T cells.

Reproducible proliferative responses of salamander ( Ambystoma mexicanum) lymphocytes cultured with mitogens in serum-free medium

There are several reports that proliferative responses (tritiated thymidine incorportation ( 3HTdR)) of salamander splenocytes cultured with phytohemagglutinin-P (PHA) or concanavalin A (Con A) in 1% fetal bovine serum (FBS)-supplemented medium are either statistically insignificant or never approach the magnitude typically observed in similarly treated cultures of frog lymphocytes. The present study confirms these findings, but also reports highly significant and reproducible PHA-induced proliferation of axolotl splenocytes and thymocytes when the medium is supplemented with 0.25% bovine serum albumin (BSA) rather than 1% FBS. In one study, splenocytes from six of six axolotls cultured in BSA-supplemented medium displayed a dose-dependent response to PHA with stimulation indices (SLs) ranging from 4.2 to 14.1. In contrast, SLs of PHA-treated cells from the same animals, cultured in parallel in FBS-supplemented medium, ranged from 0.8 to 3.0. In a kinetic study (cells harvested from days 3–7), maximal proliferation in BSA-supplemented medium was noted after 5 days; cells cultured in parallel in FBS-containing medium were not responsive to the mitogen at any time point. Although axolotl splenocytes do not exhibit PHA-stimulated growth in FBS-supplemented medium, they are reproducibly stimulated in this serum-containing medium by phorbol 12-myristate, 13-acetate (PMA). This suggests that FBS may interfere with (or does not support) some early step(s) in lectin-induced signalling, rather than with proliferation itself.

Optimum Conditions for the Chicken Lymphocyte Transformation Test

Optimum conditions for chicken (Gallus gallus) lymphocyte transformation tests were determined. Thrice-washed chicken buffy-coat cells obtained after slow centrifugation (40 x g for 10 minutes) responded substantially better to mitogenic stimulation than lymphocytes isolated on separation media containing Ficoll. Maximum responses were obtained with 2 x 10(7) lymphoid cells/ml. Responses to the mitogens were greatest when fetal bovine serum was used at a 5% concentration or pooled chicken serum and autologous plasma were used at a 1.25% concentration. Optimum mitogen concentrations varied with individual birds, timing of the culture, temperature of incubation, and serum concentration in the cultures. When 1.25% chicken serum was used in the cultures, responses were usually greatest with final concentrations of 30-50 micrograms/ml of concanavalin A (Con A) and 30-50 micrograms/ml of phytohemagglutinin-P (PHA-P). The optimum concentration of pokeweed mitogen (PWM) varied from 1 to 40 micrograms/ml among the birds and was practically impossible to establish in general. The incubation in humidified air with 5% CO2 was significantly better at 40 C than at 37 C. The total culture time of 40 hours including pulsing with 3H-thymidine during the final 16 hours of incubation was the best for Con A- and PHA-P-stimulated cells, whereas a longer incubation of 64 hours gave the highest results with PWM stimulations.

The autocrine role of tumor necrosis factor in the proliferation and functional differentiation of human lymphokine-activated T killer cells (T-LAK) in vitro

The autocrine role of tumor necrosis factor α (TNF) in the proliferation and functional differentiation of human lymphokine-activated T-killer cells (T-LAK) in vitro was investigated. Human peripheral blood lymphocytes initially stimulated with IL-2 and phytohemagglutinin-P (PHA) for 48 h will proliferate for long periods in vitro in the presence of IL-2. These T-LAK cells have been shown to be 95% CD3 positive. Employing ELISA techniques, greater than 500 pg/ml of TNF was found to be released in the supernatants of these cells during the first 5 days of culture. However, the levels dropped to 100–200 pg/ml by days 7–10. T-LAK cells grown from days 7 to 10 in the presence of IL-2 and rabbit anti-TNF were significantly growth inhibited (up to 23%). The cytolytic activity of T-LAK cells grown from days 0 to 7 in the presence of anti-TNF was also decreased (up to 75%). Phenotypic analysis of these anti-TNF treated T-LAK cells revealed a decrease in CD8 expression (up to 12%) and increase in CD4 expression (up to 27%) when compared with control cells. The data suggest that TNF has a regulatory role in the growth and functional differentiation of these human T-LAK cells.

In vivo neurotoxin administration alters immune responses in chickens ( Gallus domesticus)

1. 6-Hydroxydopamine (6-OHDA) administered in ovo enhanced in primary immune response to sheep red blood cells (SRBC) in chicks 2. Splenic norepinephrine levels increased during the peak anti-SRBC response. 3. Cell-mediated immunity as measured by delayed-type hypersensitivity to phytohemagglutinin-P (PHA-P) was not affected by treatment with 6-OHDA.

Optimum Conditions for the Turkey Lymphocyte Transformation Test

Optimum conditions for turkey lymphocyte transformation tests were determined. Thrice-washed turkey buffy-coat cells obtained after slow centrifugation (40 x g, 10 minutes) responded well to mitogenic stimulation. Turkey lymphocytes isolated on Ficoll-containing separation media largely lost their ability to respond to mitogens. Maximum responses were obtained with 2 x 10(7) lymphoid cells/ml. Responses to the mitogens were greatest when bovine fetal serum was used at a 2.5% concentration or pooled turkey serum and autologous plasma were used at a 1.25% concentration. Higher concentrations of turkey serum or plasma decreased the responses when sub-optimum doses of concanavalin-A (Con A) or phytohemagglutinin-P (PHA-P) were used. Serum-free cultures gave higher stimulation indices than cultures with serum only when sub-optimum doses of Con A or PHA-P were used. Optimum mitogen concentrations varied with individual birds, timing of the culture, temperature of incubation, and serum concentration in the cultures. Responses were usually greatest with final concentrations of 5 micrograms Con A/ml, 10 micrograms PHA-P/ml, and 20 micrograms pokeweed mitogen (PWM)/ml and when the cultures were incubated in 96-well microplates at 40 C in humidified air with 5% CO2 for 40-42 hours with pulsing with 3H-thymidine during the final 16 hours of incubation.

Development of reconstituted mouse embryos produced from bisected and electrofused pronuclear-stage embryos

The present study was designed to investigate the in vitro and in vivo development potential of reconstituted mouse embryos produced by bisection and electrofusion of pronuclear stage embryos (PN-E). Pronuclear-stage ICR and F1 (C57BL × CBA) strain mouse embryos were bisected manually with a fine glass needle under the dissecting microscope to produce karyoplasts (KP) and cytoplasts (CP). The KP of ICR PN-E and CP of F1 PN-E (KP: ICR + CP:F1) or the KP of F1 PN-E and CP of F1 PN-E (KP:F1 + CP:ICR) were attached using phytohemagglutinin-P (PHA-P) and then electrofused. High fusion rates of the KP and CP of PN-E were obtained (93.5%). The fused embryos were encapsulated in alginate gel and cultured for 72 or 96 hours. The cleavage rates of reconstituted embryos were also high (98.8%). Developmental rates to the blastocyst stage in vitro for the 96-hour culture of reconstituted embryos were 68.9% (KP:ICR + CP:F1) and 78.4% (KP:F1 + CP:ICR). Furthermore, the developmental ability of reconstituted embryos in vivo was investigated, and some live young were obtained (KP:ICR + CP:F1, 7.5% and KP:F1 + CP:ICR, 10.8%). In this study, it was confirmed that reconstituted embryos produced by bisection and electrofusion of pronuclear stage embryos were able to develop into blastocysts in vitro and into live young in vivo.

Functional assessment of cellular non-specific and specific immunity in selected healthy elderly

Thirteen healthy elderly were selected according to a simplified SENIEUR admission protocol including clinical, hematological and biochemical parameters. The goal of this protocol was to limit the influence of diseases and/or medications on the assessment of immune functions in the elderly. Plasma zinc levels of healthy elderly were comparable to those of young subjects. Cellular nonspecific immunity was determined by measuring chemiluminescence (CL) of peripheral blood granulocytes activated by opsonized zymosan particles. CL of granulocytes from healthy elderly was delayed in comparison to that of young controls when autologous serum was used. Lymphocyte proliferation induced by phytohemagglutinin-P (PHA-P) or zinc chloride (ZnCl(2)) in a serum free medium was lower in the elderly than in young controls. Preincubation of lymphocytes with ZnCl(2) before PHA-P stimulation did not restore the impaired proliferative activity of cells from old donors.

Immune Response of Chicks Fed Various Levels of Zinc

Five experiments were conducted to determine the effects of zinc intake on the immune response of chicks. Ancona chicks (Experiment 1), New Hampshire (Experiment 2), New Hampshire × Leghorn (Experiment 3), and broiler chicks (Experiments 4 and 5) were fed semipurified (Experiments 1, 2, 3, and 4) or corn and soybean meal diets (Experiment 5) containing from 8 to 88 μg zinc/g of diet An extra group of chicks in Experiments 1, 2, and 4 were fed a diet adequate in zinc but at an intake similar to that of chicks fed the lowest zinc level in each respective experiment.Low zinc intake (less that 28 μg zinc/g of diet) suppressed body weight at all times measured. The effect of zinc intake on the size of lymphoid tissues was variable, but at 5 wk of age, chicks fed 8 μg zinc/g of diet had smaller bursae of Fabricius and thymi than those fed additional zinc. Zinc intake had no influence on the primary and secondary immune response to SRBC or delayed hypersensitivity to phytohemagglutinin-P (PHA) or human gamma globulin in Ancona and broiler chicks. However, zinc intake did have a small effect in chicks from the New Hampshire parents. In Experiments 1, 2, and 4 (at least at certain times), antibody titers were reduced in pair-fed chicks. Thus, although zinc supplementation at the levels of practical diets did not affect immune function, feed restriction did.

Physiological responses of mares to short term confinement and social isolation

Summary Thirty-six pastured mares, blocked by age and temperament, were assigned to one of three housing treatment groups: pasture (P); confinement stalls (C), allowing social contact; and isolation stalls (ISS), allowing no contact with conspecif- ics. Forty-eight hours post-placement on treatment, the mares were injected intmdermally with a solution of.1 mg phytohe- magglutinin-P (PHA) in .1 ml saline in one side of the neck. After 65 h on treatment, each mare was fitted with a jugular cannula from which a blood sample was drawn and analyzed for plasma concentrations of thyroid hormones and cortisol, complete blood cell counts, and differential leukocyte counts. Blood hemoglobin was elevated for ISS mares, and mean corpuscular hemoglobin content (MCHC) was depressed for ISS mares. Interactions (P .10) in leukocyte counts, but trends were evident. The dermal response to PHA had a treatment by age interaction (P .75 was administered via the jugular cannula. Plasma cortisol concentrations from blood samples drawn 20, 40, 60, 80, 100, 120,150, 180, and 210 min post ACTH administration were then integrated to determine adrenal function (AF). No differences in AF were found (P 4 ) and triiodothyronine (T 3 ), although for C and ISS mares the concentrations of these hormones were higher than the normal values reported in the literature. Concentrations of 3, 3, 5'triiodothyronine (rT 3 ) were higher in ISS mares than in C and P mares. Physiological data suggest that C and ISS mares exhibited evidence of a mild stress reaction with increasing c0nfmement and isolation.

Generation of stimulated, lymphokine activated T killer (T-LAK) cells from the peripheral blood of normal donors and adult patients with recurrent glioblastoma

Peripheral blood mononuclear cells (PBM) from normal donors and patients with recurrent glioma were activated initially for 48–72 h with phytohemagglutinin-P (PHA) and recombinant human interleukin-2 (IL-2), and then proliferated in vitro for up to 5 months with IL-2. These cells are termed mitogen-stimulated lymphokine-activated T killer (T-LAK) cells. We measured patterns of T-LAK cell growth, in vitro cytolytic activity on a panel of continuous and primary tumor cells, and the phenotypes of the cells in these cultures. Lymphocyte viability declined dramatically over the first 3–5 days; and then the remaining cells in these cultures began to divide and maintained a constant 30–36 h doubling time for long periods in vitro. Phenotyping revealed that cells in the initial few days of culture were heterogeneous, but became almost totally CD3 T cells after 7–10 days in culture. The T-LAK cells from individual normal donors and cancer patients demonstrated a non-genetically restricted cytolytic ability against a panel of both continuous cell lines and primary autologous and allogeneic glioblastoma cells in vitro. This technique provides a method of generating large numbers of autologous cytolytic T cells with non-restricted anti-tumor activity that can be derived from peripheral blood mononuclear cells.

Suppression of interleukin-2 production and activity by factor(s) released by peripheral blood mononuclear cells during papillomavirus infections.

Supernatant fluids from cultured peripheral blood mononuclear cells (PBMC) obtained from patients with extensive papillomavirus infections such as condyloma acuminatum (CA) and epidermodysplasia verruciformis (EV) depressed the proliferative responses of T cells to phytohemagglutinin-P (PHA-P) and the production of interleukin-2 (IL-2) from those preparations. Fluids from the same cultures also inhibited the mitogenic activity of IL-2 on CTLL-2 cells as IL-2-dependent target cells. These soluble suppressor factors (SSF) from PBMC were present in significantly higher concentrations in fluids from cultured PBMC from patients in comparison to healthy controls. A soluble suppressor factor was characterized also from cultured rabbit PBMC after the rabbits had been infected with Shope papillomaviruses. This suppressor factor likewise inhibited IL-2 production and IL-2 activity.

Role of endogenously produced interleukin-6 as a second signal in murine thymocyte proliferation induced by multiple cytokines: Regulatory effects of transforming growth factor- β1

Previous studies have demonstrated that murine thymocytes proliferate in the presence of submitogenic concentrations of phytohemagglutinin-P (PHA-P) and various cytokines such as interleukin-1 (IL-1), interleukin-4 (IL-4), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). We report that C3H/HeJ thymocytes stimulated with PHA-P and IL-1, IL-4, or TNF-α secrete significant levels of IL-6 as determined on B9 hybridoma cells. The possibility that thymocyte proliferation induced by these cytokines was mediated through IL-6 was investigated utilizing a neutralizing monoclonal antibody against murine IL-6, MP5 20F3.1. The results demonstrate that MP5 20F3.1 inhibited the proliferative response of thymocytes and B9 hybridoma cells to recombinant MuIL-6 (but not HuIL-6) and neutralized the endogenous IL-6 produced in the thymocyte cultures, but did not have any measurable effects on the proliferative responses induced by IL-1, IL-4, or TNF-α. Although the level of endogenously produced IL-6 did not play a measurable role in the proliferative response induced by TNF-α, the addition of higher concentrations of IL-6 augmented the proliferation of murine thymocytes induced by rMuTNF-α. In addition, recombinant human transforming growth factor- β 1 (rHuTGF- β 1) significantly inhibited thymocyte proliferation induced by HuIL-1, rMuIL-4, rMuIL-6, and rMuTNF-α. The studies suggest that IL-1, IL-4, or TNF-α mediate a proliferative signal on murine thymocytes independent of IL-6 and that the proliferative signals provided by these cytokines as well as IL-6 are inhibitable by rHuTGF- β 1.

Effect of in vitro selenium repletion on bovine lymphocyte proliferation

Deficient or toxic levels of selenium (Se) are known to impair immune function. Peripheral blood mononuclear cells (PBMC) were isolated from Holstein heifers of adequate Se status. PBMC were plated at densities of 0.5, 1.0, and 2.0 × 10 5 cells/well in 96-well microtiter plates and stimulated with T-cell mitogens, concanavalin A (ConA) and phytohemagglutinin-P (PHAP), and pokeweed mitogen (PWM), a T-dependent B-cell mitogen. Sera incorporated into the incubation system were from two newborn calves born to Se-deficient dams and averaged 20 ng Se/ml. Se additions of 50-400 ng/ml resulted in significant enhancement of PWM-stimulated proliferation relative to controls (no added Se). Enhancement of proliferation was cell density dependent, occurring predominately at a density of 0.5 × 10 5 cells/well. In contrast, proliferative responses of PBMC to ConA and PHAP were generally not enhanced by repletion with the lower levels of Se. Supplementation with higher levels of Se (1600–3200 ng/ml) inhibited proliferative responses to all mitogens tested regardless of cell density in culture. In summary, repletion with physiological levels of Se selectively stimulated B-cell proliferation an effect which was dependent on cell density.

Comparison of Phytohemagglutinin-Induced Cutaneous Hypersensitivity Reactions in the Interdigital Skin of Broiler and Layer Chicks

Cutaneous basophil hypersensitivity (CBH) responses elicited by intradermal injection of phytohemagglutinin-P (PHA-P) were evaluated in the interdigital skin of broiler and layer chicks. Five- and 10-day-old broiler and layer chicks were injected intradermally in the interdigital skin between the third and fourth digits of the right foot with 25, 50, or 100 micrograms of PHA-P. The PHA-P-elicited CBH responses were evaluated by determining interdigital skin thickness before injection and 12 and 24 hr after injection. The effect of treatment with the T-lymphocyte-suppressing drug cyclosporin on the CBH responses was determined in chicks treated daily for 4 days before skin-testing at 10 days of age. Injection of PHA-P caused significant increases (P less than 0.005) in skin thickness at all dose amounts, with the maximum CBH response elicited by 100 micrograms PHA-P. The CBH response was significantly higher (P less than 0.05) in broilers than in layers. Treatment with cyclosporin significantly suppressed (P less than 0.01) the CBH response in 10-day-old chicks of both types. Results indicate that the interdigital skin-test is a rapid, simple means of assessing normal and suppressed T-lymphocyte-mediated immune response in broiler and layer chicks.