Photoperiod controls the induction,retention, and retrieval of antigen-specific immunological memory

Changes in day length affect several measures of immunity in seasonally breeding mammals. In Siberian hamsters (Phodopus sungorus), short day lengths suppress specific secondary antibody responses to the keyhole limpet hemocyanin (KLH) antigen and enhance cutaneous delayed-type hypersensitivity (DTH) responses to dinitrofluorobenzene (DNFB). These experiments tested whether day length affects secondary antibody and DTH responses by altering immune function solely during the interval after the initial exposure to each antigen, solely during the interval after the second exposure, or during both stages of the respective immune responses. Adult male Siberian hamsters were exposed to either a long (16 h light/day; LD) or a short (8 h light/day; SD) photoperiod for 7.5 wk before receiving an initial exposure to each antigen (KLH injection, cutaneous DNFB treatment; separate groups of animals for each antigen). A subset of LD hamsters was transferred to the SD photo-period, and a subset of SD hamsters was transferred to the LD photoperiod. Other hamsters remained in LD or SD. Eight weeks later, all hamsters were challenged with a second subcutaneous injection of KLH or a second application of DNFB to the ear, and immune responses were measured. Exposure to SD during the primary antibody response did not affect secondary IgG responses, but SD exposure during the secondary response significantly suppressed IgG production independent of day length during the initial KLH treatment. In contrast, exposure to SD during the DNFB challenge enhanced the ensuing DTH response, but this enhancement depended on the photoperiod prevailing during the initial exposure. Exposure to SD during the sensitization stage did not enhance DTH in hamsters subsequently exposed to LD. The data suggest that short photoperiods have enduring effects on immune responsiveness and on the establishment and retention of immunological memory.     

Potentiation of the rat delayed-type hypersensitivity reaction by the Fc portion of human IgG1

Fc fragments derived from a human IgG1 myeloma protein potentiate the rat delayed-type hypersensitivity (DTH) reaction to antigen challenge. Lewis rats immunized with heat-killed tubercle bacilli give augmented DTH reactions to the purified protein derivative of tuberculin when Fc fragments are included in the challenge dose. Similar potentiation of DTH by pFc' fragments indicates that the active site is located in the CH3 domain of IgG1. Histologic evaluation of the augmented reaction sites revealed predominantly mononuclear cell infiltrates characteristic of DTH reactions. Skin tests of tubercle bacilli-sensitized rats with an unrelated antigen and/or Fc fragments fail to elicit significant reactions. Augmentation of the DTH reaction to purified protein derivative is restricted to the Fc or pFc' region fragments since intact monomeric IgG1, Fab fragments, and bovine serum albumin were all shown not to be active potentiators. The DTH reaction of ovalbumin-sensitized rats was similarly augmented when Fc fragments were included with a challenge dose of ovalbumin, thus supporting the general nature of the phenomenon. These results support the concept of Ig molecules as multifunctional proteins that can not only serve effector functions but also participate in the regulation of immune responses.     

Studies with protein kinase C inhibitors presently available cannot elucidate the role of protein kinase C in the activation of NADPH oxidase

The effects of various protein kinase C (PKC) inhibitors on NADPH oxidase (NO) activation by the phorbol ester PMA and by the chemotactic peptide FMLP were studied. H-7 reduced the effects of both stimuli in human neutrophils (HN) and HL-60 cells by 13-63%. Polymyxin B did not inhibit NO activation by PMA and FMLP in HN and reduced the effects of both stimuli in HL-60 cells by 27-55%. Retinal and retinoic acid enhanced the effects of PMA and FMLP in HL-60 cells and of FMLP in HN up to 4.5-fold. In contrast, retinoic acid inhibited the effect of PMA in HN. In the presence of cytochalasin B, retinal inhibited the effect of FMLP in HN, whereas retinoic acid inhibited NO activation by FMLP in both cell types. The dual PKC/calmodulin inhibitors trifluoperazine and W-7 abolished NO activation by PMA and FMLP in HN and HL-60 cells. Thus, the effects of PKC inhibitors on NO activation exhibit (1) cell type specificity, (2) stimulus dependency and (3) no correlation with in vitro inhibition of PKC. Our results suggest that studies with PKC inhibitors presently available cannot clarify the role of PKC in NO activation.     

Suppression of delayed-type hypersensitivity to oxazolone in whole-body-irradiated mice and protection by WR-2721

The effect of whole-body irradiation on cellular immunity, as measured in vivo by delayed-type hypersensitivity (DTH) to oxazolone (4- ethoxymethylene -2-phenyl- oxazol -5-one), was determined in CD2F1 mice. DTH, determined by changes in ear swelling after challenge with oxazolone, was significantly depressed in irradiated mice (500-900 rad of 60Co) in a dose-dependent fashion when animals were irradiated after sensitization and before challenge with oxazolone. Administration of WR-2721 [S-2-(3-aminopropylamino)ethylphosphorothioic acid] 30 min before irradiation (2 days after sensitization) resulted in protection against suppression of DTH, which was dependent on drug and radiation dose. An effective dose of WR-2721 (200 mg/kg body wt) provided an approximate dose-modifying factor of 1.3. The data suggest that WR-2721 interacts with cells involved in that DTH response (lymphocytes and/or macrophages) and that WR-2721 may be useful in protecting against radiation-induced decrements in cell-mediated immunity.     

Selective induction and inhibition of direct and lectin-dependent cell-mediated cytotoxic reactivity

The immune reactivity of mice (C57BL/6, H-2^b) which had been challenged with various numbers (10²–10⁸) of allogeneic tumor cells (P815, H-2^d) was assessed at various times after challenge. Challenge with a high dose (10⁸) of tumor cells resulted in the development of direct cytotoxicity (DCMC), lectin-dependent cytotoxicity (LDCC), delayed-type hypersensitivity (DTH), and antibody production, whereas challenge with lower doses (< 10⁶) of tumor cells favored development of DTH and LDCC with marginal or no DCMC or antibody production. Spleen cells from low-dose alloimmune animals failed to produce DCMC when cultured with P815 cells in vitro and were capable of nonspecifically suppressing the DCMC response of normal spleen cells in MLC. Treatment with cyclophosphamide (100 mg/kg) prior to alloimmunization did not alter the pattern of DTH and cytotoxic reactivity, although treatment after alloimmunization was immunosuppressive for all forms of reactivity. When low-dose challenge was followed by cyclophosphamide treatment and a subsequent high-dose challenge, selective inhibition of DTH, LDCC, and suppressor activity, but not DCMC, was observed. The data suggest that (a) the initial challenge dose plays a significant role in determining which effector and regulatory populations will be activated and what direction the expression of immune reactivity will take; (b) the activated responding populations of DTH, DCMC, and LDCC effector cells are sensitive to cyclophosphamide treatment, whereas the precursors of each are resistant to the effects of the drug; (c) low-dose alloimmunization may be used in combination with cyclophosphamide treatment to modulate DTH, DCMC, and LDCC reactivity in a selective manner; (d) the cytotoxic effector cells responding to highdose challenge and mediating DCMC and those responding to low-dose challenge and mediating LDCC appear to arise from distinct precursor populations.     

Delayed-type hypersensitivity response in an isogenic murine model of paracoccidioidomycosis

The specific delayed-type hypersensitivity (DTH) response was evaluated in resistant (A/SN) and susceptible (B10.A) mice intraperitoneally infected with yeasts from a virulent (Pb18) or from a non-virulent (Pb265)Paracoccidioides brasiliensis isolates. Both strains of mice were footpad challenged with homologous antigens. Pb18 infected A/SN mice developed an evident and persistent DTH response late in the course of the disease (90th day on) whereas B10.A animals mounted a discrete and ephemeral DTH response at the 14th day post-infection. A/SN mice infected with Pb265 developed cellular immune responses whereas B10.A mice were almost always anergic. Histological analysis of the footpads of infected mice at 48 hours after challenge showed a mixed infiltrate consisting of predominantly mononuclear cells. Previous infection of resistant and susceptible mice with Pb18 did not alter their DTH responses against heterologous unrelated antigens (sheep red blood cells and dinitrofluorobenzene) indicating that the observed cellular anergy was antigen-specific. When fungal related antigens (candidin and histoplasmin) were tested in resistant mice, absence of cross-reactivity was noted. Thus, specific DTH responses againstP. brasiliensis depend on both the host's genetically determined resistance and the virulence of the fungal isolate.Abbreviations DTH delayed-type hypersensitivity - DNFB dinitrofluorobenzene - FN18 Fava Netto's antigen obtained from isolate Pb18 - FN265 Fava Netto's antigen obtained from isolate Pb265 - SRBC sheep red blood cells     

Delayed-type hypersensitivity to Babesia microti-infected erythrocytes in mice

Strong delayed-type hypersensitivity (DTH) to Babesia microti was elicited when intraerythrocytic parasites (IEP) were inoculated subcutaneously into the flank of normal mice 6 to 14 days before challenge in the ipsilateral footpad with 10(8) IEP. Intraperitoneal or intravenous administration of antigen did not sensitize mice for DTH. When challenge was given 21 days after immunization, the response was approximately half of the maximum and then rose again slowly over the next 3 weeks to levels that were not significantly different from those maximal values. The response was similar in seven strains of mice, regardless of sex. The response was classified as a true DTH reaction on the basis of kinetics, histology, and the transfer of responsiveness with immune T lymphocytes of the Ly 1+ phenotype, but not with serum. The reaction was specific for IEP since control groups given two injections of red blood cells from uninfected syngeneic mice (NRBC) or one injection of NRBC or sheep red blood cells (SRBC) and one of IEP never developed significant footpad swelling. Freed parasites obtained by osmotic rupture, density gradient sedimentation, and lethally irradiated IEP were also effective for elicitation of DTH. Anti-IEP DTH was expressed in a dose-dependent fashion with 10(6), 10(7), or 10(8) parasites sufficing for immunizing inoculum as long as 10(8) parasites were used as the challenge dose. Mice immunized and challenged with 10(8) lethally irradiated IEP (60 krad, 60Co), were protected against subsequent intraperitoneal challenge with 10(8) viable IEP. If mice were infected intraperitoneally with 10(8) IEP at any time between 21 days before immunization to 2 hr after challenge, their ability to respond to immunization and challenge was profoundly depressed. These data suggest that development of a strong anti-parasite DTH response can occur in parallel with resistance to infection, but is not a rapid sequela of bloodborne infection.     

Contact hypersensitivity: a simple model for the characterization of disease-site targeting by liposomes

A murine model of delayed-type hypersensitivity (DTH) is characterized with respect to liposome accumulation at a site of inflammation. Mice were sensitized by painting the abdominal region with a solution of 2,4-dinitrofluorobenzene (DNFB) and inflammation was induced 5 days later by challenging the ear with a dilute solution of DNFB. The inflammatory response was readily monitored by measuring ear thickness (edema) and radiolabeled leukocyte infiltration. Maximum ear swelling and cellular infiltration occurred 24 h after the epicutaneous challenge with the ear returning to normal size after approximately 72 h. We demonstrate that large unilamellar vesicles (LUV) accumulate at the site of inflammation to a level more than 20-fold higher than that measured in the untreated ear. Vesicle delivery to the ear correlated with increased vascular leakage resulting from endothelium remodeling in response to DNFB challenge, and was not a consequence of increased local tissue blood volume. Extravasation occurred only during the first 24 h after ear challenge; after this time the permeability of the endothelium to vesicles returned to normal. We further showed that LUV with a diameter of 120 nm exhibit maximum levels of accumulation, that a polyethylene glycol surface coating does not increase delivery, and that the process can be inhibited by the application of topical corticosteroids at the time of induction. These data and the inflammation model are discussed with respect to developing lipid-based drug delivery vehicles designed to accumulate at inflammatory disease sites.     

Calmodulin inhibitors suppress calcium signaling from serotonin receptors in smooth muscle cells and abolish vasoconstrictive response on intravenous introduction of serotonin

Comparative study of the effect of calmodulin inhibitors trifluoperazine, W-12, and W-13 and the TRPV1 channel blocker capsazepine on receptor-dependent calcium metabolism in smooth muscle cells of the rat aorta and on the contraction of the isolated rat aorta was performed. Trifluoperazine almost completely abolishes an increase in free cytoplasmic calcium concentration in smooth muscle cells isolated from the rat aorta and smooth muscle cells of the A7r5 line in response to serotonin and does not affect cellular reaction to vasopressin and angiotensin II. W-12 and W-13 also do not attenuate responses to vasopressin and angiotensin II and reduces by two times free cytoplasmic calcium concentration elevation in response to serotonin. The efficiency of calcium metabolism suppression by calmodulin inhibitors correlates with the degree of inhibition of the aorta contractile response to serotonin. It was demonstrated that the inhibitory action of calmodulin antagonists on calcium metabolism in smooth muscle cells and the contractility of the isolated rat aorta during the activation of serotonin vasoconstrictive receptors are realized by a TRPV1-independent mechanism. It was demonstrated in experiments in vivo that trifluoperazine does not influence hypotensive reaction in rats (normally observed in response to intravenous serotonin injection), but removes the hypertensive effect of this neurotransmitter in rats after chronic introduction of dexamethasone. The results obtained confirm the hypothesis (that we previously stated) about the direct involvement of calmodulin in signal transmission from vasoconstrictive serotonin receptors.     

Delayed-type hypersensitivity to allogeneic mouse epidermal cell antigens

Footpad swelling response was used to measure the alloantigenicity of epidermal cells (ECs) in delayed-type hypersensitivity (DTH). Strong footpad swelling was oberserved 3 h after the challenge, and it continued for 48 h after the challenge. Genetical incompatibility between the recipients and the ECs was required to induce significant footpad swelling. H-2 or non-H-2 incompatibility between mice and ECs in the sensitization phase sufficed to develop significant footpad swelling. Incompatibility caused by point mutation in the A region induced strong responses when B6. C-H-2 ^bm12 mice were immunized with B6/J ECs, but the disparity in immuno-globulin h (Igh) allotype genes was insufficient. H -Y antigen on ECs could also elicit the DTH response. Semiallogeneic F₁-derived ECs sensitized the parental recipients. The responses were successfully transferred by immune lymph node cells, but not by immune sera. Treatment of these immune lymph node cells with monoclonal antibodies plus complement revealed that the cells responsible for DTH transfer were Lyt-1⁺2^–, Ia^– T cells.Abbreviations used in this paper DNFB 2,4-dinitro-1-fluorobenzene - DTH delayed-type hypersensitivity - ECs epidermal cells - HBSS Hanks' balanced salt solution - MHC major histocompatibility complex - PBS phosphate-buffered saline     

Pretreatment with caerulein protects against memory impairment induced by protein kinase C inhibitors in the rat.

The effect of subcutaneously injected caerulein (CER) on memory impairment induced by protein kinase C (PKC) inhibitors, H-7 and melittin, was examined in rats. Intracerebroventricular injection of PKC inhibitors caused marked memory impairment in one-trial passive avoidance response and Morris water tank tasks. However, when rats were pretreated with CER at a subcutaneous dose of 1 microgram/kg 3 hours before the training trials, the reduced latency of the passive avoidance response was significantly increased, and in the Morris water pool tasks the memory deficit induced by PKC inhibitors completely disappeared. These results indicate that CER can offer protection against the effect of PKC inhibitors at least from the viewpoint of the memory processes.     

The effect of IgE-mediated mast cell degranulation on the expression of experimental contact sensitivity in the mouse

The effects of mast cell activation/degranulation on the elicitation of contact sensitivity (CS) to oxazolone and dinitrofluorobenzene were investigated. Mice were actively sensitized to oxazolone by epicutaneous painting followed by ear challenge. Passive sensitization to DNFB was induced by intradermal injections of dinitrophenol (DNP)-specific cloned T cells in the ears. Mast cells in the challenged ears were activated in various time periods by inducing a passive cutaneous anaphylaxis reaction where passive sensitization with monoclonal IgE anti-DNP antibodies was followed by iv injection of DNP-BSA. This combination of immediate and delayed-type hypersensitivity reactions resulted in a significant increase of ear swelling without any noticeable effect on cellular infiltration when the contact response was evaluated a short time (3-4 hr) after mast cell activation. The very same results were obtained in naive (unsensitized) mice, indicating that this reaction was nonspecific. However, when the CS reaction was evaluated at its peak, i.e., 24 hr post challenge, mast cell activation that had been induced 0.5-11 hr after ear challenge did not have any significant effect on both swelling and cellular infiltration when the latter was evaluated by a radiometric assay. We conclude that in these systems mast cell activation/degranulation makes little or no contribution to the modulation of T-cell activity.     

Delayed-type hypersensitivity is mediated by a sequence of two different T cell activities

Classical 24- to -48 hr delayed-type hypersensitivity (DTH) skin reactions are preceded by an early skin swelling reaction that peaks 2 hr after challenge. The ability to elicit this early component of DTH is T cell dependent and is also dependent on tissue mast cells and release of serotonin, mainly from these mast cells. The current study presents pharmacologic and kinetic evidence that the late response depends on the occurrence of the early response. A variety of pharmacological agents known to deplete, prevent release of, or block the activity of serotonin, when given just before skin challenge, blocked both the early and late components of DTH, but had no effect when given (even repeatedly) after the occurrence of the early component. Thus, the serotonin-dependence of the 24-hr component of DTH represents a dependence on the early component in which serotonin release is required. A temporal dependence of the late component of DTH on the early component was also demonstrated. The early and late phases occur at different times in recipients of sensitized T cells, depending on the interval between transfer and challenge, but there is a fixed 10- to 12-hr gap. Delayed onset of the late component occurs in recipients challenged immediately after transfer and appears to be due to a delay in the onset of the early component. This delay can be abolished by adoptive cell transfer into mice that are able to elicit a normal early component because of prior transfer of T cells that are able to mediate just an early component. On the basis of these findings, we conclude that DTH consists of a cascade of events. T cells mediating the early aspect of DTH release antigen-specific factors that, upon encountering antigen activate local serotonin-containing cells, such as mast cells, to release serotonin, which opens gaps between adjacent endothelial cells. Through these interendothelial gaps a second T cell population enters the extravascular space and interacts with local antigen to induce the late response by releasing the chemoattractant lymphokines that are classically associated with DTH and that cause recruitment of bone marrow-derived circulating leukocytes to infiltrate the reaction site. The ability of the second T cell population to mediate the late component of DTH is independent of further release of serotonin.     

Contribution of protein kinase A and protein kinase C signalling pathways to the regulation of HSD11B2 expression and proliferation of MCF-7 cells

Contribution of the protein kinase A (PKA) and protein kinase C (PKC) signalling pathways to the regulation of 11beta-hydroxysteroid dehydrogenase type II (HSD11B2) gene expression was investigated in human breast cancer cell line MCF-7. Treatment of the cells with an adenylyl cyclase activator, forskolin, known to stimulate the PKA pathway, resulted in an increase in HSD11B2 mRNA content. Semi-quantitative RT-PCR revealed attenuation of the effect of forskolin by phorbol ester, tetradecanoyl phorbol acetate (TPA), an activator of the PKC pathway. It was also demonstrated that specific inhibitors significantly reduced the effect of activators of the two pathways. Stimulation of the PKA pathway did not affect, whereas stimulation of the PKC pathway significantly reduced MCF-7 cell proliferation in a time-dependent manner. A cell growth inhibitor, dexamethasone, at high concentrations, caused a 40% decrease in proliferation of MCF-7 cells and this effect was abolished under conditions of increased HSD11B2 expression. It was concluded that in MCF-7 cells, stimulation of the PKA signal transduction pathway results in the induction of HSD11B2 expression and that this effect is markedly reduced by activation of the PKC pathway. Activation of the PKC pathway also resulted in inhibition of cell proliferation, while activation of the PKA pathway abolished the antiproliferative effect of dexamethasone. These effects might be due to oxidation of dexamethasone by the PKA-inducible HSD11B2.     

Effects of suramin on the immune responses to sheep red blood cells in mice. I. In vivo studies

The effect of Suramin on the cell-mediated delayed-type hypersensitivity (DTH) and the humoral immune responses elicited in mice by sheep erythrocytes was studied. The results show that administration of Suramin, at various times before or after antigenic sensitization, results in a profound inhibition of cell-mediated responses but has no adverse effect on antibody production. Suramin was particularly effective when given during the effector phase of DTH: mice which were treated with this drug, 4 days after immunization, at the time of skin testing, exhibit negative or low DTH responses compared to control mice. Evidence is presented that this short-term Suramin-induced suppressive effect on the expression of DTH is related to a defective recruitment, by sensitized T lymphocytes, of phagocytic cells at the site of the inflammatory reaction. In addition, when treatment with Suramin precedes by 8 days (Day -8) or by 1 hr sensitization with sheep erythrocytes for DTH, decreased DTH reactions over controls were observed. The inhibitory effect exerted by Suramin administered on Day -8 can be reversed by increasing the dose, from 10(6) to 10(8) sheep erythrocytes, of the sensitizing antigen. The possibility is discussed that, in this case, Suramin may interfere with the generation of DTH-mediating cells through a rapid degradation of antigen related to the Suramin-induced hyperplasia of the mononuclear phagocyte system. In contrast, DTH anergy in mice treated with Suramin 1 hr before sensitization is maintained regardless of the sensitizing antigen dose. Analysis of the sensitized lymphocyte population in these mice indicates that Suramin does not prevent the induction of DTH-mediating cells and suggests that the expression of these latter is inhibited by suppressive cells which are generated as a result of drug treatment.     

Contact hypersensitivity reactions to dinitrofluorobenzene mediated by monoclonal IgE anti-DNP antibodies

Several studies have suggested a possible role for IgE antibodies in the pathogenesis of cutaneous hypersensitivity reactions that reach maximum intensity 24 to 48 hr after antigen challenge. The recent availability of murine monoclonal IgE anti-hapten antibodies has made possible the direct examination of the range of cutaneous inflammatory reactions that can be mediated by such antibodies. We have examined the effects of passively sensitizing BALB/c mice with monoclonal IgE anti-dinitrophenyl (DNP) antibody 48 hr before antigen challenge. Inflammatory responses were assessed by measuring ear swelling in mice challenged on the ears with the reactive hapten 2,4-dinitrofluorobenzene (DNFB). Compared with unsensitized controls, the ears of mice passively sensitized with IgE anti-DNP displayed a biphasic pattern of ear swelling after DNFB challenge. An early, transient response (present within 15 to 30 min of challenge and returning to control levels within 4 to 9 hr) was followed by a second, more persistent increase in ear swelling that peaked 24 to 48 hr after challenge. This biphasic pattern of ear swelling seen in IgE-sensitized mice was temporally indistinguishable from that observed in mice conventionally sensitized for allergic contact dermatitis reactions by epicutaneous application of DNFB 5 days before DNFB ear challenge. Antigen specificity of the IgE-mediated contact hypersensitivity reactions was demonstrated by the failure of mice passively sensitized with IgE anti-DNP to display early or delayed ear swelling greater than unsensitized controls when challenged with either of two noncross-reacting haptens, fluorescein isothiocyanate or oxazolone. Mice passively sensitized with a monoclonal IgA anti-DNP antibody (MOPC 315) 48 hr before DNFB challenge failed to display early or delayed ear swelling greater than unsensitized controls. Heat inactivation of the IgE anti-DNP ascitic fluid at 56 degrees C for 30 min completely abolished its capacity to passively sensitize mice for contact hypersensitivity reactions after DNFB challenge. These results document the existence of an antigen-specific, IgE-mediated, delayed-in-time cutaneous hypersensitivity response that can be elicited by epicutaneous challenge (contract) with a reactive hapten.     

Prevention by the MER tubercle bacillus fraction of immunosuppression induced by cancer chemotherapeutic agents

Summary Contact hypersensitivity (CH) to 2,4 dinitro-1-fluorobenzene (DNFB) was induced in BALB/c mice by DNFB skin application. Development of skin CH was suppressed by exposure of the animals after sensitization to the cancer chemotherapeutic drugs cyclophosphamide (CY), sodium methotrexate (MTX), and 5-fluorouracil (5FU). Unresponsiveness to DNFB was also induced in parallel experiments by a single intravenous injection of dinitrobenzenesulfonate (DNBS), either before or concomitant with sensitization. Potentiation of CH skin reactivity was achieved by administration of CY prior to sensitization.Pretreatment by two injections of the methanol extraction residue (MER) tubercle bacillus fraction restored significantly the ability of animals exposed to CY, MTX, or 5FU to respond to DNFB sensitization. The agent did not impair the potentiation of CH skin reactivity that could be effected by administration of CY prior to sensitization.MER treatment was not effective in reversing hapten-induced (DNBS) tolerance in mice.These findings favor the assumption that MER, under the conditions tested, stimulates the function of positively reacting T cells and exerts no enhancing or protective action on suppressor T cells.     

Phospholipase A<Subscript>2</Subscript> Inhibitors Modulate the Effect of Trifluoperazine on the Intracellular Ca<Superscript>2+</Superscript> Concentration in Macrophages

Using Fura-2AM microfluorimetry, it was shown for the first time that phospholipase A₂ inhibitors 4-bromophenacyl bromide and glucocorticosteroids prednisolone and dexamethasone attenuate Ca²⁺ responses induced by neuroleptic trifluoperazine in macrophages. The results suggest the involvement of phospholipase A₂ and arachidonic acid metabolism cascade in the effect of trifluoperazine on intracellular Ca²⁺ concentration in macrophages.     

Regulation of contact sensitivity to DNFB in the mouse: effects of adult thymectomy and thymic factor.

The contact sensitivity response to DNFB is decreased after adult thymectomy (ATX). This response decreases to 50% of the control response of normal age-matched mice as soon as 3 weeks after ATX and is not further depressed 9 to 16 weeks after ATX. These results suggest that two T cell subsets of different lifespan are involved in the anti-DNFB response. A circulating thymic factor (FTS) is able to restore the contact sensitivity response to DNFB when injected 3 to 9 weeks after ATX but not 16 weeks later. By contrast, FTS has a depressive effect on the contact sensitivity response to DNFB of normal mice through a cyclophosphamide-sensitive T cell subset. These results suggest that FTS regulates DNFB contact sensitivity by acting on a cyclophosphamide-sensitive T cell subset, still present 9 weeks after ATX but absent after 16 weeks. Thus although the T cell defect, causing a depression of the contact sensitivity reaction to DNFB is quantitatively similar 3 and 16 weeks after ATX, its nature is probably different.