Lymphocyte Mitogenic Responses Research Articles

Acute and Chronic Effects of Superior Cervical Ganglionectomy on in vitro Mitogenic Responses of Lymphocytes from Submaxillary Lymph Nodes of Pituitary-Grafted Rats

Male rats were grafted an anterior pituitary within breast muscles or received a sham operation on day 5 of life. At the 60th day of life, the sympathetic denervation of rat submaxillary lymph nodes was achieved by a bilateral sympathetic superior cervical ganglionectomy (SCGx; at 15.00 h). Rats were killed either 18 h later (acute SCGx) or after 12 days (chronic SCGx) to measure lipopolysaccharide (LPS)- and concanavalin A (ConA)-induced cell proliferation in submaxillary lymph nodes, submaxillary lymph node cellularity and serum prolactin levels. In control rats, acute SCGx significantly augmented LPS or ConA activity on lymph cells while chronic SCGx had no effect. In pituitary-grafted rats, acute SCGx depressed the mitogenic effect of LPS or ConA whereas chronic SCGx augmented it. A global inhibitory effect of surgical stress on submaxillary lymph node cellularity was found in rats subjected to SCGx or its sham operation 18 h earlier. Serum prolactin levels increased significantly in pituitary-grafted rats, particularly in those subjected to chronic SCGx. In pituitary-grafted rats, a significant effect of acute SCGx was apparent, with serum prolactin levels augmenting about twice in sham-SCGx rats, and to a significantly less extent in acute SCGx rats. The results provide further evidence of the immunomodulatory role of local sympathetic nerves in submaxillary lymph nodes.

Treatment of Wilson's disease with zinc: XIV studies of the effect of zinc on lymphocyte function

Although administration of zinc to human subjects has been reported to interfere with lymphocyte function, this single report has never been confirmed or refuted. We have developed zinc as a lifelong therapy for patients with Wilson's disease. Interference with lymphocyte function occurring as a side effect of zinc therapy could produce serious problems in our patients. We evaluated lymphocyte mitogenic response and natural killer cell activity in patients with Wilson's disease treated for 5 years or longer with zinc, in comparison with normal controls, and found no differences. In a second study, we evaluated these same parameters in patients with Wilson's disease before and after 1 year of zinc therapy, and again found no significant differences. We have seen no indications of immune suppression or increased susceptibility to infections in our patients, who have now been treated with zinc for up to 15 years. We conclude that any side effects from compromised lymphocyte function caused by administration of zinc are not of concern to patients with Wilson's disease.

Immunotoxicity of environmentally relevant mixtures of polychlorinated aromatic hydrocarbons with methyl mercury on rat lymphocytes in vitro

AbstractThe immunosuppressive effects of methyl mercury (MH), polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐p‐dioxins (PCDDs), and dibenzofurans (PCDFs) are well established at high exposure levels but unclear at low exposure levels. We exposed Fischer 344 rat splenocytes, thymocytes, and peripheral blood lymphocytes in vitro for 72 h to MHg (0.1, 2 μg/ml), PCDD/PCDF mixtures (1, 15 pg/ml) of three PCDDs (2,3,7,8‐tetrachlorodibenzo‐p‐dioxin, 1,2,3,7,8‐pentachlorodibenzo‐p‐dioxin, and 1,2,3,4,7,8‐hexachlorodibenzo‐p‐dioxin) and two PCDFs (2,3,7,8‐tetrachlorodibenzofuran and 1,2,3,7,8‐pentachlorodibenzo‐furan), three Aroclor® (1242, 1254, 1260), PCB mixtures (0.01, 0.5 μg/ml), or combinations of MHg/PCB/PCDD/PCDF mixtures Mitogenic responses of lymphocytes to concanavalin A, phytohemagglutinin, or lipopolysaccharide/dextran sulfate were determined by 3H‐thymidine uptake; cytotoxicity and intracellular Ca2+ were determined by flow cytometry. Methylmercury (2 μg/ml and PCB/ PCDD/PCDF mixtures with 2 μg/ml MHg decreased the viability of splenocytes to 57 and 40% at 4 and 24 h, respectively. Basal intracellular calcium ion levels were unaffected by the treatments. Methylmercury suppressed the responses of lymphocytes to T and B cell mitogens. All combinations of MHg/PCB/PCDD/PCDF mixtures decreased mitogenic responses to levels similar to those to MHg alone. In contrast, PCB and PCDD/PCDF mixtures did not suppress but augmented responses of splenocytes and peripheral blood lymphocytes to T cell mitogens. Overall, no interactive toxicity was observed with MHg/PCB/PCDD/PCDF mixtures on cytotoxicity and lymphocyte mitogenic responses. Therefore, MHg may pose a greater threat than organochlorines to the mammalian immune system.

Reversal of 1,3-bis(2-chloroethyl)-1-nitrosourea-induced severe immunodeficiency by transduction of murine long-lived hemopoietic progenitor cells using O6-methylguanine DNA methyltransferase complementary DNA.

Bone marrow toxicity is a dose-limiting side effect of chloroethylnitrosourea (CNU) chemotherapeutic alkylating agents. A major determinant of CNU cytotoxicity is the methylation of guanine at the O6-position and the subsequent formation of interstrand DNA cross-links. O6-Methylguanine DNA methyltransferase (MGMT) removes alkyl groups from the O6 position of guanine and has been shown to repair CNU-induced DNA damage. We have previously demonstrated that transplantation of murine bone marrow cells transduced with a recombinant retroviral vector expressing MGMT via the human phosphoglycerate kinase promoter (PGK-MGMT) protects animals in vivo from acute myelotoxicity associated with CNU treatment. In the present study, we examined the effects of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), a commonly used CNU, on long term recovery of the lymphoid compartment, including thymus reconstitution, peripheral T and B cell populations, and lymphocyte mitogen responses in mice reconstituted with PGK-MGMT-transduced hemopoietic cells. Mice transplanted with either mock-infected control or PGK-MGMT-transduced stem cells were treated with five weekly doses of BCNU. Analysis of the lymphoid compartment demonstrated significant damage 3 mo after the last BCNU dose in control animals. In contrast, the profound deficiency in CD4+CD8+ double-positive thymocytes and mature lymphocytes observed in control mice surviving BCNU treatment was completely reversed in mice transplanted with PGK-MGMT-transduced bone marrow and was associated with molecular evidence of in vivo selection of transduced cells in the lymphoid compartment. Thus, long term immunodeficiency following CNU therapy may be prevented by genetic modification of murine hemopoietic stem cells with MGMT, leading to significant improvement in post-transplant immune function.

セレニウム・ビタミンE投与妊娠牛の周産期における好中球ニトロブルー・テトラゾリウム還元能およびリンパ球幼若化能

セレニウム・ビタミンE投与妊娠牛の周産期における好中球ニトロブルー・テトラゾリウム還元能およびリンパ球幼若化能

Intracerebroventricular injection of interleukin-1 suppresses peripheral lymphocyte function in the primate.

The cytokine interleukin-1 (IL-1) can act within the brain to induce peripheral endocrine and immune effects. In the rodent intracerebroventricular (i.c.v.) injection of IL-1 activates the hypothalamic-pituitary-adrenal axis and suppresses peripheral immune function by a CRH-dependent mechanism. It is unknown if IL-1 can similarly act within the brain to cause peripheral immunosuppression in the primate and to what extent this could be attributed to the IL-1-induced increase in ACTH and cortisol levels. In this study we have characterized the pituitary-adrenal and peripheral lymphocyte responses to IL-1 alpha (4.2 micrograms) infused over 30 min into the lateral ventricle of ovariectomized monkeys (n = 5) as compared with responses to an intravenous (i.v.) ACTH infusion (1 microgram/h for 7 h; n = 4). Four serial blood samples were obtained for ACTH and cortisol determination and for lymphocyte isolation during a 1-hour baseline and for 7 h after IL-1 or ACTH. Lymphocyte proliferation was measured by 3H-thymidine uptake in response to stimulation with phytohemagglutinin. In all 5 animals, IL-1 alpha caused rapid and profound suppression of lymphocyte mitogen responsiveness for 7 h. Baseline lymphocyte proliferation was 51,800 +/- 9,780 cpm and suppressed to a nadir of 4.5% with a mean of 23% baseline over 7 h (p < 0.001). Mean ACTH and cortisol levels increased from 33 +/- (SEM) 4.6 pg/ml and 43 +/- 4.0 micrograms/dl, respectively, during the control period to 90 +/- 14 pg/ml and 56 +/- 2.6 micrograms/dl, respectively, after IL-1 (p < 0.01). Before i.v. ACTH, baseline lymphocyte proliferation was 49,400 +/- 2,820 cpm, and suppressed to a mean of 64% of baseline during ACTH infusion (p < 0.05). Mean ACTH and cortisol levels increased from 48 +/- 5.0 pg/ml and 43 +/- 2.0 micrograms/dl, respectively, to 170 +/- 34 pg/ml and 66 +/- 2.3 micrograms/dl, respectively, during the ACTH infusion (p < 0.01). Lymphocyte suppression after i.c.v. IL-1 was much more profound than after i.v. ACTH (p < 0.01); the area under the IL-1 response curve was 37% of the area under the ACTH response curve. These studies demonstrate for the first time in the primate that centrally injected IL-1 has a profound suppressive effect on lymphocyte function. They also show for the first time in any species that there appears to be a significant immunosuppressive message produced by i.c.v. IL-1 that is not accounted for by the associated increases in ACTH and cortisol.

Roles of Basigin, a Member of the Immunoglobulin Superfamily, in Behavior as to an Irritating Odor, Lymphocyte Response, and Blood–Brain Barrier

Basigin is a transmembrane glycoprotein belonging to the immunoglobulin superfamily. Using the knockout mouse lacking the basigin gene (Bsg), we analyzed the function of basigin in adult mice lacking the gene [Bsg(-/-)]. Although histochemical studies on the localization of basigin (also called HT7 and neurothelin) strongly indicated that it is involved in the function of the blood–brain barrier, basigin knockout mice showed only a little difference, if any, to wild-type mice in the function of the blood brain–barrier. The mitogenic response of lymphocytes upon mixed lymphocyte reaction was greater inBsg(-/-) mice. Finally,Bsg(-/-) mice repeatedly visited filter paper impregnated with acetic acid or isozine, indicating an abnormality in either reception of the odor or behavior as to it.

Beta-blockade enhances adrenergic immunosuppression in rats via inhibition of melatonin release

We have recently shown in rats that an in vivo treatment with catecholamines via α 2,-receptors leads to a pronounced suppression of T-and B-cell mitogen responses of peripheral blood lymphocytes (PBL), provided that a β-blocker is administered concomitantly. Since melatonin (MEL) reportedly has stress-protective effects on several immune functions, and since the release of MEL from the pineal gland is inhibited by β-blockade, we tested the effect of MEL substitution on T-and B-cell mitogen responses of PBL in rats treated with two s.c. implanted retard tablets containing noradrenaline (NA) and propranolol. It was found that an oral treatment with MEL (about 40 /j,g/animal) abolished the adrenergic immunosuppression. Furthermore, functional pinealectomy induced by constant light had a similar enhancing effect on the α 2adrenergic immunosuppression as observed with β-blockers, whereas PBL from animals kept at the regular light/dark interval were resistant to the treatment with the selective α 2agonist clonidine. It is concluded that endogenous MEL effectively protects rat PBL from adrenergic immunosuppression, and that β-blockers enhance the immunosuppressive property of os-adrenergic agents via blocking the night-time release of MEL.

The effect of strenuous exercise, calorie deficiency and sleep deprivation on white blood cells, plasma immunoglobulins and cytokines.

Moderate exercise appears to stimulate the immune system, but there is good evidence that intense exercise can cause immune deficiency. In the present study the authors examined the effect of continuous physical exercise (35% of VO2 max), calorie deficiency and sleep deprivation on the immune system of young men participating in a 5-7 days military training course. There was a two-three fold increase of neutrophils from day 1, the values remained high and decreased slightly at the end of the course. Monocyte counts also increased with a pattern similar to that of neutrophils. Eosinophils decreased to 30% of control and lymphocyte numbers decreased by 30-40%. All the major subgroups (CD4 T cells, CD8 T cells, B cells, NK cells) were reduced. Neutrophil function, as tested by measuring chemotaxis, was significantly stimulated during the first days of the course, in particular in the group with the lowest calorie intake. The mitogenic response of lymphocytes to PHA and Con A was variable, ranging from stimulation during one course to no effect in another course. Serum levels of immunoglobulins decreased significantly during the course. IgG was reduced by 6-7%, IgA by 10-20% and IgM by 20-35%. The authors found no changes of interleukin 1, 2 and 4 during the course, but a (12-20%) reduction (P less than 0.01) of interleukin 6, and an increase (P less than 0.01) of granulocyte-macrophage colony stimulating factor. Altogether the results from the ranger course present a mixed-up picture. The non-specific phagocyte-related immunity was enhanced. On the other hand, the data indicate that even a moderate physical activity, around the clock, caused significant suppression of a number of parameters reflecting the status of the specific, lymphocyte-related immunity. It is noteworthy, however, that there was no significantly increased infection rate during the course or in the first 4-5 weeks thereafter.

Seasonal variations in the immune system of the tench, Tinca tinca (Cyprinidae): proliferative response of lymphocytes induced by mitogens

The proliferation of tench lymphocytes induced by mitogens was studied during the four seasons of the year. Fish were maintained under natural conditions of photoperiod and temperature (mean ± SD: 12±2°C in winter, 22±3°C in spring, 30±3°C in summer and 21±3°C in autumn). Cultures were performed in vitro at 22°C in all seasons and the results were compared. Subsequently, in seasons with extreme water temperatures, cultures in vitro were performed at the same temperature as that of the water (12°C in winter and 30°C in summer) and the results were compared seasonally at the “seasonal temperature”, i.e. at 22°C in spring, 30°C in summer, 22°C in autumn and 12°C in winter. Phytohemagglutinin, concanavalin A, lipolisaccharide from E. coli and pokeweed mitogen were used as mitogens. Studies performed at 22°C as assay temperature in all seasons showed profound seasonal changes: while in spring, summer and autumn the mitogenic response of lymphocytes to phytohemagglutinin, concanavalin A, lipolisaccharide from E. coli and pokeweed mitogen was very low, during winter the results obtained were significantly higher. However, when the assays were performed at the corresponding “seasonal temperature” the differences were not as pronounced between the different seasons, and the mitogenic responses of lymphocytes were found to be the lowest during the winter and the highest during the summer with all mitogens used. This fact suggests that immunosuppression occurs in winter and an immunostimulation occurs in summer. However, the higher response found in winter when assaying at 22°C suggests that this property of lymphocytes needs an assay temperature higher than the in vivo temperature in order to observe accurate mitogenic responses.

Altered Switch in Lipid Composition During T-Cell Blast Transformation in the Healthy Elderly

Decreased mitogen responsiveness of lymphocytes during aging correlates inversely with membrane microviscosity, which reflects an altered lipid composition. Therefore, we addressed the question, whether age-related alterations of lipid metabolism affect the switch in lipid composition during formation of blasts. Membrane lipids and fatty acids of peripheral blood lymphocytes from SENIEUR protocol compatible ("healthy") elderly donors (66-77 yr) and young controls (18-30 yr) were quantified after incubation with or without the mitogen phytohaemagglutinin. The blastic change in membrane lipid composition was different for young controls with respect to cholesterol, phosphatidylethanolamine, total phospholipids, as well as several fatty acids. Moreover, the age-related alterations in the switch of membrane lipids and fatty acids were significantly correlated with a decreased mitogen response. Thus, the alterations in membrane reorganization during blast formation of lymphocytes from the elderly point to a disturbed cellular lipid homeostasis with possible impact on the age-related reduction in immune function.

Evaluation of immune parameters in depressed patients

The association between depression and altered immunological activities has repeatedly been suggested, but experimental data show contradictory results. In this work, cellular and humoral immunological activities were evaluated in patients presenting major depression, unipolar subtype. Natural killer cell activity (NKCA) was significantly reduced in patients as compared to healthy controls ( p < 0.001). However, lymphocyte mitogenic responses and immunoglobulin titers (IgG, IgM, and IgA) were similar for all samples. Hematological, hormonal, and nutritional variables presented normal values in patients and in controls. A familial history of depression was related to lower NKCA and higher phytohemagglutinin responses ( p < 0.01). These data suggest possible differential inhibition of cellular immune responses in depressed patients.

Immunologic aspects of vigabatrin treatment in epileptic children.

Vigabatrin (VGB) is an antiepileptic drug (AED) that acts by irreversibly inhibiting gamma-aminobutyric acid transaminase (GABA-T). To evaluate immune responses to GVG, we studied 29 idiopathic or symptomatic epileptic children and also examined a control group (n = 15). Epileptic children were tested before and after 1 and 3 months of VGB treatment. Whole blood was used to connect subsets with commercial monoclonal antibodies. Peripheral blood mononuclear cells (PBMC) were used to assess natural killer (NK) cell activity and lymphocyte response to phytohemagglutinin (PHA) and concavalin A (Con A). Immunoglobulin (Ig) levels were tested in serum. At baseline, no immunologic abnormalities were observed in either control or treated patients. During treatment, the percentage and absolute number of B lymphocytes, serum concentration of Ig, number of T total mature lymphocytes (CD3), T-rosetting lymphocytes (CD11), T-helper cells (CD4), and mitogenic response of lymphocytes remained unchanged. Several other immunologic responses showed a statistically significant increase after 1 and 3 months of VGB treatment, however, including the percentage and absolute number of T-suppressor cells (CD8) and NK cells and NK cell activity. The correlation between number of NK cells and NK cell activity was significant. Data obtained demonstrated that VGB may interfere with the modulation of the immune system, especially cytotoxic cell populations.

Immune functions of spleen lymphocytes of rats subjected to chronic irradiation and antioxidant (ubiquinone Q-9) diet.

The dynamics of T and B cell immunity in spleens from rat exposed to whole-body chronic irradiation with dose rates of 12.9 cGy/day (range 1-10 Gy) and 3.0 cGy/day (range 0.57-2.04 Gy) were investigated. gamma-irradiation with a dose-rate of 12.9 cGy/day was shown to produce a wave-like suppression of the T lymphocyte mitogenic response. Irradiation with a dose-rate of 3.0 cGy/day caused a decrease in immune response of T lymphocytes 48 days after onset of exposure (total dose 1.4 Gy). It was also shown that chronic irradiation with a dose-rate of 3.0 cGy/day produced significant changes in the DNA of T lymphocytes. Our results show that the radiation-induced suppression of immune functions and damage to DNA structure were partially eliminated when animals were fed a daily diet supplemented with a natural antioxidant, ubiquinone Q-9. The inhibiting effect of chronic irradiation was more pronounced in B lymphocytes because of their higher radiosensitivity.

Long-term lipid-based total parenteral nutrition activates mononuclear cells and modulates membrane lipid composition in pigs.

In previous studies we have found lung granulomas in pigs on long-term soybean-based total parenteral nutrition (TPN). In the present study we have investigated activities and membrane lipids of cells known to participate in a granulomatous process. Pigs were given TPN with soybean emulsion for 7 weeks, controls were given saline intravenously and consumed a similar caloric load in a standard oral diet. Spontaneous nitroblue tetrazolium (NBT) reduction increased 204% in peripheral blood mononuclear cells (MNC) from TPN animals compared to controls (p < 0.05), and 161% (p = 0.05) in alveolar macrophages. The spontaneous lymphocyte mitogen response (LMR) rate in MNC increased 299% (p < 0.05). Endotoxin-stimulated procoagulant activity in MNC tended to increase in TPN animals. Acid phosphatase and lysozyme production in alveolar macrophages were not significantly changed. The serum neopterin level at the end of the observation was 7.0 nmol l-1 in TPN animals compared to 3.9 nmol l-1 in controls (p < 0.01), while interleukin-1 and tumour necrosis factor were not detectable. These findings indicated in vivo activation of peripheral blood monocytes, lymphocytes and alveolar macrophages in pigs on TPN. The membrane lipid contents of linoleic acid (18:2, n-6) increased, while arachidonic acid (20:4, n-6) tended to decrease both in MNC and lung tissue. Thus, linoleic acid conversion did not lead to accumulation of arachidonate in the cell membranes. Direct effects on monocytes, lymphocytes and alveolar macrophages of TPN particles, and altered cell membrane function, due to linoleic acid enrichment, are tentative explanations for the raised cell responses. Such cell activation may have contributed to the formation of granulomas.

The role of macrophages in increased mitogen response of rat splenic lymphocytes following in vitro incubation with vitamin E.

The role of macrophages (M phi) in the enhancement of lymphocyte proliferation by alpha-tocopherol (VE) was investigated using rat splenocytes. The proliferation of whole splenocytes was significantly higher than that of M phi-depleted splenocytes at all concentrations of concanavalin A (Con A; 0.5-10 micrograms/ml). When whole and M phi-depleted splenocytes were preincubated with VE (2 micrograms/ml) for 24 h, the proliferation of whole splenocytes was significantly enhanced compared to that of whole splenocytes preincubated with medium alone. In contrast, M phi-depleted splenocytes did not show any increase of proliferation following in vitro pretreatment with VE. When the splenic: M phi pretreated with both VE (2 micrograms/ml) and Con A (10 micrograms/ml) for 24 h were further incubated with splenic lymphocytes, their proliferation was significantly enhanced compared to that of splenic lymphocytes cultured with splenic M phi pretreated with Con A. In this experiment, the medium containing 2-mercaptoethanol (2-ME) had the ability to enhance splenic lymphocyte proliferation, which masked the enhanced effect of VE on splenic: lymphocyte proliferation. Furthermore, in vitro treatment of VE could not decrease the production of prostaglandin E2, but could enhance the production of interleukin 1 from splenic M phi. These results suggest that M phi play an important role in the proliferation of splenic lymphocytes following in vitro incubation with VE, which is closely associated with the action of VE as an immunomodulator rather than antioxidant.

Estrogen effects on lymphoid tissue in neonatal and adult female mice.

Outbred female mice of the NMRI strain were treated with daily doses of diethylstilbestrol (DES; 0.1-10 micrograms), estradiol-17 beta (E2; 5 micrograms), testosterone (T; 5 or 25 micrograms), progesterone (P; 100 micrograms), corticosterone (CC; 10 or 50 micrograms), or olive oil (controls) for the first 5 days after birth. Animals were killed on day 6 after birth, at 2, 4, and 8 weeks or at 4 and 6 months. Only CC resulted in reduced thymus index weight (IW, mg organ weight/g body weight) on day 6 while the estrogen-induced reduced IW was secondary to a reduced body weight. Four-week-old and older estrogen-treated females had increased thymus IW (1.8-fold at 8 weeks after 5 micrograms DES/day neonatally) which was still seen at 6 months. Estrogen-induced thymus enlargement also occurred in 8-week-old inbred NMRI females and in females belonging to the BALB/c strain. Thymus IW in 8-week old T-, P- and CC-treated females was as in controls. The leukocyte counts in blood and bone marrow were lower in DES females than in controls. The responses (thymus IW, peripheral blood leukocyte count) of 8-week-old females to ovariectomy and challenge with DES were different in DES females and in control females. The mitogen response of spleen lymphocytes and thymocytes was similar in controls and DES females. An anomaly in the hypothalamic-pituitary-gonad-thymus axis of adult, neonatally estrogen-treated females might explain the thymus enlargement.

Mechanisms whereby macrophage-derived nitric oxide is involved in morphine-induced immunomodulation.

In vivo administration of morphine, whether acute or chronic, produces numerous alterations of immune status in both animals and humans. For instance, our laboratory and others demonstrated in rodent studies that morphine treatment produces a suppression of the mitogenic responsiveness of lymphocytes from the spleen and blood, a decrease in cytokine production by stimulated splenocytes, a depression of splenic natural killer cell activity, and a decrease in primary antibody responses.1,2,3 The means by which morphine produces immune alterations are unclear, but probably involve several systems within the organism, including the central nervous system, the autonomic nervous system and the neuroendocrine system, depending upon the immune compartment and immune measure being investigated and whether morphine is administered acutely or chronically.1,2,4

Phototoxicity of Quinolones: Measurement by UV-A Inhibition of Concanavalin A-Stimulated Lymphocyte Mitogenic Response

Phototoxicity of ten quinolones was measured by inhibition of concanavalin A-stimulated mitogenesis (measured by [3H]-thymidine uptake) of guinea pig splenocytes after UV-A irradiation in the presence of drug. At a drug concentration of 2.5μg/ml and a radiation dose of 3.9J/cm2, inhibition rates (expressed as percentage of uptake, without irradiation) were: lomefloxacin (LFLX), 51%; fleroxacin (FLRX), 34%; ciprofloxacin (CPFX) and enoxacin (ENX), 27%; norfloxacin (NFLX), 25%; ofloxacin (OFLX), 19%; piromidic acid (PA), 13% tosufloxacin (TFLX), 12%; pipemidic acid (PPA), 11%; and levofloxacin (LVFX, an optical isomer of OFLX), 8%. At a concentration, of 25 μg/ml, on the other hand the phototoxic activity of quinolones decreased in the order LFLX, CPFX, ENX, FLRX>NFLX>LVFX, PA, OFLX>PPA. These results suggest that LFLX, with a fluorine attached to the 8 position, is strongly photoxic, although it shows low cytotoxicity (measured by inhibition of incorporation in the dark), against splenocytes. UV-A irradiation of solutions of LFLX and FLRX blue-shifted the absorption maximum from 280 nm to 270 nm and decreased the optical density between 325 and 340 nm. Although CPFX, ENX, NFLX, OFLX, LVFX and PA also showed optical density decreases at 260–290 nm and 325–350 nm, the maximal absorption did not shift. There were no changes in the absorption spectra of PPA and TFLX even after UV-A irradiation at a dose of 7.8J/cm2. Thus, quinolones phototoxicity and the spectral changes produced by UV-A irradiation appear to be related.

T lymphocyte development and function in dogs with X-linked severe combined immunodeficiency.

Canine X-linked severe combined immunodeficiency disease (XSCID) is characterized by a failure to thrive, thymic dysplasia, and a lack of a T lymphocyte mitogenic response. As in human XSCID, affected dogs in our colony have a mutation in the IL-2R-gamma gene. This mutation dramatically altered T lymphocyte development, because XSCID thymi were severely reduced in size and cellularity, contained an increased proportion of immature CD4-CD8- thymocytes, a decreased proportion of intermediate CD4+CD8+ thymocytes, and a normal proportion of CD4+CD8- and CD4-CD8+ thymocytes. XSCID thymi were also deficient in the percentage of CD3-L+ thymocytes. Interestingly, several XSCID dogs had normal percentages of CD3-L+ PBL. Although the mutation did not interfere with IL-2 production, PHA-activated XSCID PBL demonstrated severely diminished IL-2 binding and were nonresponsive to IL-2. These results indicate that the lack of a functional IL-2R-gamma chain in dogs with XSCID primarily affects developing CD4-CD8- thymocytes as they acquire the cell surface Ag CD3-L and interferes with the ability of peripheral T lymphocytes to bind and respond to IL-2.