Phenotypic and functional heterogeneity of human T lymphocytes producing B-cell growth factor(s): a clonal analysis

Human T cells active on B-cell proliferation are phenotypically and functionally heterogeneous. A series of 43 human T-cell clones, selected according to their ability to release factors active on B-cell proliferation, were analyzed. B-Cell proliferation was evaluated by two different assays, namely, a costimulation assay with anti-mu antibody or by an assay based on B-cell preactivation with Staphylococcus aureus. Eight of these clones expressed the T4-/T8+ phenotype while the remaining were T4+/T8-. The large majority had T-cell growth factor activity as well. However, some clones appeared to have B-cell growth factor activity only. Fourteen clones (eight T8+ and six T4+) also displayed cytolytic activity in a phytohemagglutinin-dependent cytolytic assay.

A pilot study of the pharmacokinetics and triglyceride lowering activity of acipimox in dialyzed uremic patients

The pharmacokinetics of acipimox was studied in 6 dialyzed uremic patients given single oral doses of 50 mg. Acipimox was not significantly eliminated outside dialysis, whereas during dialysis it was efficiently cleared with plasma, t 1/2 is about 2.6 hours. Accordingly, a dosage schedule of 50 mg or 100 mg of acipimox after each dialysis session was selected for a second, 4-week study in 14 uremic patients with hypertriglyceridemia. Acipimox plasma levels, monitored during the study, proved in agreement with those expected on a theoretical pharmacokinetic basis. A clear-cut reduction of serum triglyceride levels was also achieved.

In vitro synthesis of human IgE: reappraisal of a 5-year study

In the last 5 years some models of human IgE production in vitro have been investigated in our laboratory. Spontaneous IgE synthesis was found in cultures of B cells from most patients with atopic dermatitis or atopic patients with multiple sensitivities and from some patients with pollenosis, but only during the pollination period. A small and variable increase of the spontaneous IgE synthesis was induced by soluble factor(s) produced by T cells from patients with severe atopy. Selected helper T cell clones were also able to induce IgE synthesis in vitro by both atopic and normal B cells.

Radioimmunoassay of acipimox in human plasma and urine

A radioimmunoassay was developed for the determination of acipimox (5-methylpyrazinecarboxylic acid 4-oxide) in human plasma and urine. Acipimox was conjugated to bovine serum albumin through a spacer with 4 carbon atoms, and repeatedly injected into rabbits. Antisera raised in these animals were highly specific and virtually no cross-reaction was observed with 5-methylpyrazinecarboxylic acid and nicotinic acid. Despite the low specific activity of the labelled antigen used, concentrations of acipimox in human plasma and urine as low as 40 ng/ml could be determined. The intra- and inter-assay coefficients of variation ranged between 4.32-6.25% and 6.19-11.55% respectively, and mean recovery of the compound spiked to plasma was 100-103%. The method was applied to determine plasma levels and urinary excretion of acipimox after oral doses of 150 mg and 250 mg to four volunteers.

Frequent coexpression of cytolytic activity and lymphokine production among human T lymphocytes. Production of B cell growth factor and interleukin 2 by T8+ and T4+ cytolytic clones

These studies were designed to determine the degree of overlapping between cytolytic function and lymphokine production among peripheral blood human T lymphocytes. T8+ and T4+ cells were obtained by sorting purified T cells using the fluorescence-activated cell sorter (FACS) and cloned at 0.25 cells/well in a microculture system that allows clonal growth of every T cell. 49/49 T8+ clones but only 5/102 T4+ clones displayed cytolytic activity, as assessed by a lectin-dependent assay. Cytolytic clones were further analyzed for their ability to release interleukin 2 (IL2) and B cell growth factor(s) (BCGF) upon 24 h stimulation with phytohemagglutinin. Fifteen percent and 18% of T8+ cytolytic clones were producing IL2 and BCGF, respectively; in addition 3 out of 5 T4+ cytolytic clones released both lymphokines. Although the majority of cytolytic clones producing IL2 were also producing BCGF, 5 clones released either BCGF or IL2. The present studies indicate that the coexpression of cytolytic and helper/inducer functions is relatively common among peripheral blood T lymphocytes, irrespective of their T8+ or T4+ phenotype.

Surface markers and function of circulating thyroid autoantibody-producing cells

The in vitro synthesis of antithyroglobulin (anti-Tg) and antithyroid microsomal (anti-M) autoantibodies by peripheral blood mononuclear cells (MNC) from patients with autoimmune thyroid diseases was investigated using sensitive immunoradiometric assays. Cultures were carried out in the presence or in the absence of pokeweed mitogen (PWM). Thyroid autoantibodies were undetectable in supernatants of MNC cultures from 9 normal subjects. Supernatants of MNC cultured without PWM had detectable levels of anti-Tg and anti-M in 5 (19.3%) and in 2 (7.7%) of 26 patients with autoimmune thyroid diseases, respectively. In the presence of PWM, a marked increment in the antibody concentrations occurred in all but 1 of these cultures, and the number of positive cultures increased to 13 (50.1%) for anti-Tg and to 15 (57.7%) for anti-M. Studies of MNC fractions depleted of T lymphocytes (non-T cells) were carried out on selected patients showing antibody synthesis only after PWM stimulation. Autoantibody production was not found with non-T cells, but the effect of the mitogen was restored by readdition of T cells. Irradiation (1000 rad) of T cells before coculturing significantly enhanced autoantibody production. With this model no significant functional difference was found between autologous and allogenic T cells from thyroid autoimmune disease patients or from normal subjects. The cells involved in PWM-driven thyroid autoantibody synthesis, as defined by depletion studies, were lymphocytes bearing DR antigens and surface immunoglobulin G (IgG) without detectable surface immunoglobulin M (IgM). Depletion from MNC suspensions of Tg-binding cells abolished PWM-stimulated anti-Tg production, but did not alter the synthesis of anti-M. Further studies were carried out on MNC from a single patient with Hashimoto's thyroiditis, whose non-T cells consistently produced large amounts of anti-M and total IgG in the absence of PWM. The addition of PWM to these unfractionated MNC slightly increased the production of anti-M, but inhibited antibody synthesis after depletion of T lymphocytes. Interestingly, the addition of autologous T lymphocytes to non-T cells inhibited the spontaneous synthesis of anti-M. These data indicate that in vitro synthesis of anti-Tg and anti-M by MNC may be frequently induced by stimulation with PWM in patients with thyroid autoimmune disorders. PWM-stimulated synthesis of thyroid autoantibodies appears to be T-cell dependent and modulated by radiosensitive T lymphocytes. The cells responsible for PWM-dependent thyroid autoantibody synthesis are B lymphocytes with surface membrane IgG and have receptors specific for the autoantigen.(ABSTRACT TRUNCATED AT 400 WORDS)

Displacement of T lymphocytes with the 'Helper/Inducer' phenotype from peripheral blood to lymphoid organs in untreated patients with Hodgkin's disease

A panel of previously characterized monoclonal antibodies: B67.6, OKT3, OKT4, B53.4, Leu3a, OKT8, Leu2a, OKM1, M12 and B52.1 were used as a probe to assess mononuclear cells in peripheral blood (PB), lymph nodes (LN) and spleens of untreated patients with Hodgkin's disease (HD). The mean % and absolute number of T lymphocytes were significantly decreased in PB of HD patients when compared with control values. Reduction of circulating T lymphocytes reflected the selective loss of cells showing the 'helper/inducer' ('H/I') phenotype. In fact, a lower number of these cells was demonstrated in HD patients with advanced disease and, even though to a lesser extent, in those with localized disease. In contrast, decreased values of T cells with the 'cytotoxic/suppressor' ('C/S') phenotype were only found in patients with advanced disease, showing pan-lymphocytopenia. Unlike PB, LN and spleens involved by HD usually showed increased %s of T lymphocytes, especially of those possessing the 'H/I' phenotype. The displacement of T lymphocytes with 'H/I' phenotype from PB to lymphoid organs further supports the possibility of a chronic immune response against abnormal cells or unknown antigens in the affected organs of patients with HD.

Abnormalities of in vitro immunoglobulin synthesis by peripheral blood lymphocytes from untreated patients with Hodgkin's disease

The immunoglobulin-synthesizing activities of peripheral blood mononuclear cells from 57 untreated patients with Hodgkin's disease and 47 normal subjects were compared. Cumulative amounts of IgM and IgG synthesized and secreted by unstimulated and pokeweed mitogen-stimulated cells over a 7-d period were determined in a solid-phase radioimmunoassay. Synthesis of IgM in unstimulated cultures and of both IgM and IgG in cultures stimulated with pokeweed mitogen was markedly reduced in patients with Hodgkin's disease, whereas the mean level of the spontaneous IgG synthesis was enhanced. The degree and frequency of in vitro abnormalities were not influenced by disease stage or histology. Depression of pokeweed mitogen-induced immunoglobulin synthesis did not correlate with excessive number of monocytes and it was unaffected by removal of phagocytic cells or addition to the cultures of monocytes from normal individuals. On the other hand, monocytes isolated from blood of patients with Hodgkin's disease were even more effective than normal monocytes in supporting pokeweed mitogen-induced immunoglobulin synthesis by normal phagocyte-depleted mononuclear cells. Synthesis of both IgM and IgG induced by pokeweed mitogen remained subnormal after addition to patient B cell cultures of autologous irradiated T cells or allogeneic normal T lymphocytes. T cells from patients with Hodgkin's disease appeared at least as effective as normal T cells in helping pokeweed mitogen-induced immunoglobulin production by normal B cells. However, when normal T cells were co-cultured with B cells from patients with Hodgkin's disease, spontaneous IgG synthesis declined, whereas the addition of patient T cells to normal B cells resulted in an increase of spontaneous IgG synthesis. In patients showing depression of pokeweed mitogen-induced immunoglobulin synthesis the lymphoproliferative response and immunoglobulin synthesis stimulated by Staphylococcus aureus bacteria of the Cowan first strain, a T cell independent B cell mitogen, were also markedly reduced. These studies demonstrate impairment of immunoglobulin synthesis by cultured lymphocytes from untreated patients with Hodgkin's disease after stimulation with polyclonal B cell activators and suggest that the in vitro abnormalities may be, at least in part, the result of a preexisting in vivo activation of lymphocytes in Hodgkin's disease patients.

IgE synthesis in vitro induced by T cell factors from patients with elevated serum IgE levels

The effect of unstimulated T cell culture supernatants (TCS) from patients with atopic dermatitis and high serum IgE levels on the IgE production in vitro by B cell rich suspensions from normal individuals or grass pollen sensitive patients with mild atopy was evaluated. TCS from patients with raised IgE enabled B cell suspensions from normal individuals to produce detectable amounts of IgE and potentiated the spontaneous IgE synthesis in vitro by B cell suspensions from grass sensitive patients. In contrast, the addition of TCS from normal subjects with low serum IgE levels did not increase or even reduced IgE synthesis by B cell cultures. When the same B cell cultures were analysed for their ability to produce IgG or IgM protein, no significant differences were observed. These findings indicate that T lymphocytes from patients with high serum IgE levels can release soluble factor(s) possessing isotype (IgE) specific potentiating activity.

In vitro selective expansion of allergen specific T cells from atopic patients

Peripheral blood mononuclear cells from atopic donors were stimulated in vitro with allergens (Rye group I or Dermatophagoides pteronyssinus). T cell lines were originated and maintained in long term culture using IL-2 and periodical restimulations with allergen. The lines were antigen specific (i.e. responded to the allergen used to raise them and not to other antigens) and required that the antigen was presented by autologous cells (i.e. they were restricted). The restriction elements were probably at the level of HLA-DR antigens since the proliferative response was specifically blocked by anti-HLA-DR antibodies. Surface marker analysis revealed that the lines comprised mainly cells with an helper/inducer phenotype, although cells with markers of the suppressor/cytotoxic T cells were also present. The lines could be cloned by limiting dilution and clones with the same restriction and specificity as the parental line were isolated. These studies demonstrate the possibility of obtaining a large number of allergen specific human T cells that can be used for further in vitro studies on the regulation of the IgE response.

Phenotypic and functional characterization of a Sézary cell

We have studied the surface antigen pattern, enzymatic phenotype, and functional capacity of peripheral blood lymphocytes from a patient with Sézary syndrome (SS). The majority of these cells formed E rosettes but lacked the Fc(mu) receptor. The neoplastic cells were reactive with pan-T cell (OKT3)- and helper T cell (OKT4)-subset monoclonal antibodies; however, they lacked the 5/9 antigen, which identifies a more restricted subset of helper T cells. Most SS cells also reacted with PTF 29.12, a monoclonal antibody which recognizes DR determinants. Only 35% of the cells expressed single, focal accumulations of alpha-naphthyl-acid esterase activity, which is a characteristic of T.M cells, but 85% of them showed this focal staining pattern with acid phosphatase or beta-glucuronidase. Mononuclear cells from the SS patient showed poor or no proliferative response to phytohemagglutinin, pokeweed mitogen, concanavalin A, purified protein derivative, Candida, and allogeneic cells and lacked both helper and suppressor activity for pokeweed mitogen driven production of IgM and IgG immunoglobulins by normal B cells, but they were able to stimulate a marked proliferative response in mixed-lymphocyte culture. The defective expression of enzymatic and surface membrane characteristics, together with the lack of some T-cell functions, suggests that the patient cells may be immature T.M lymphocytes.

In vitro production of IgE by human peripheral blood mononuclear cells. III. Demonstration of a circulating IgE-bearing cell involved in the spontaneous IgE biosynthesis

The presence of surface membrane IgE (SmIgE)-bearing cells in the peripheral blood (PB) of atopic patients was investigated by the use of isotype-specific rosettes of human red blood cells coupled to immunosorbent-purified rabbit or monoclonal mouse antibodies against human IgE (R or M anti-epsilon-HRBC). After dissociation of cell bound IgE by treatment with acid buffer, 2.1 +/- 0.3% and 1.2 +/- 0.3% circulating non-T, non-phagocytic, cells from atopic patients were still capable of forming rosettes with R or M anti-epsilon-HRBC, respectively. IgE molecules detectable on cells after dissociation of cytophilic IgE were quite resistant, like surface membrane IgM (SmIgM), to treatment with proteolytic enzymes, but they were removed under capping conditions by soluble anti-IgE antisera. All SmIgE-bearing (IgE+) cells also bore DR determinants, but many of them lacked SmIgM. Depletion of IgE+ cells strongly reduced the ability of PB lymphocyte suspensions from atopic patients to produce spontaneously IgE protein in vitro. Likewise, depletion of cells bearing DR determinants (DR+ cells) resulted in a marked decrease of the spontaneous IgE biosynthesis, whereas depletion of SmIgM-bearing (IgM+) cells had no effect. These data suggest that cells mainly implicated in the spontaneous IgE production in vitro seen in atopic patients are DR+ IgE+ IgM- circulating lymphocytes.

In vitro production of IgE by human peripheral blood mononuclear cells. IV. Modulation by allergen of the spontaneous IgE antibody biosynthesis

Peripheral blood lymphocytes (PBL) from a proportion of grass-sensitive patients, studied during or immediately after the grass pollination period, showed spontaneous production in vitro of grass-specific IgE antibody, whereas PBL from atopic patients sensitive to allergens other than grass pollens or non-atopic individuals did not. Pre-incubation of IgE antibody producing PBL from grass-sensitive patients with minute amounts of a mixed grass pollen (MGP) extract or Rye grass antigen Group I (Rye I) usually resulted in a reduction of the spontaneous production in vitro of IgE protein and in a marked inhibition of the spontaneous production in vitro of grass-specific IgE antibody. This antigen-specific inhibition was not mediated by T lymphocytes, but it was apparently due to a signal directly delivered by antigen to the spontaneously IgE antibody producing cells. The results support the concept that the activity of cells responsible for the persistent IgE antibody formation in vitro in atopic patients can be modulated by antigen.

Effect of vitamin E deficiency on rabbit intramuscular collagen

The effect of a vitamin E-deficient diet on muscular collagen was studied in young rabbits. Intramuscular collagen content was found to increase in vitamin E-deficient rabbits, both in absolute and relative values, while no changes in urinary hydroxyproline excretion were observed. The overall solubility of intramuscular collagen was higher and the collagen soluble in guanidine hydrochloride was richer in alpha-chains. Such findings would suggest that avitaminosis E induces the production of new intramuscular collagen.

Protein A reactivity of lymphocytes from some patients with chronic lymphocytic leukaemia mediated by an interaction with the F(ab')2 region of surface immunoglobulin

Peripheral blood lymphocytes (PBL) from 15 of 38 patients with chronic lymphocytic leukaemia (CLL) were capable of forming rosettes with human erythrocytes coated with staphylococcal protein A (SpA-HRBC). PBL from seven patients also showed a marked proliferative response after stimulation with Staphylococcus aureus bacteria strain Cowan I (Cowan Staph). The SpA-rosetting of CLL cells was inhibited by incubation with F(ab')2 fragments of anti-immunoglobulin (Ig) antibodies. In addition, incubation with these fragments inhibited the proliferative response of leukaemic B cells to Cowan Staph. The Cowan-Staph induced proliferation of CLL cells was also impaired by the addition of normal human IgG and human IgG F(ab')2 fragments to the cultures, whereas non-immune rabbit IgG was not inhibitory. The inhibitory activity of human IgG F(ab')2 fragments was retained by a SpA-Sepharose column, and it was found in the material recovered from the same column by acid elution. These data indicate that an interaction between SpA and a structure located in the F(ab')2 region of surface Ig of different classes is responsible for either SpA-binding or the Cowan-Staph-induced proliferative response of PBL from some patients with CLL.

Surface immunoglobulins are involved in the interaction of protein A with human B cells and in the triggering of B cell proliferation induced by protein A-containing Staphylococcus aureus

The nature of surface components responsible for the reactivity of a subset of human B cells with staphylococcal protein A (SpA) was studied. The ability of normal non-T cells or non-T cells from patients with chronic lymphocytic leukemia (CLL) to form rosettes with human red blood cells coated with SpA (SpA-HRBC) was strongly inhibited or abolished by incubation with F(ab')2 fragments of antibodies against human immunoglobulin (Ig), whereas the incubation with F(ab')2 fragments of antibodies against a non-Ig cell surface antigen, such as beta 2-microglobulin, had no effect on the SpA-rosetting of human lymphocytes. The role of the reaction between surface Ig (sIg) and SpA in the triggering of the proliferative response induced by Staphylococcus aureus bacteria strain Cowan I (Cowan Staph) on normal or leukemic non-T cells was also investigated. A parallelism was observed between the mitogenic activity on normal human non-T cells of Cowan Staph and F(ab')2 fragments of immunosorbent-purified rabbit antibodies to human mu-chain. On the other hand, monovalent Fab fragments of anti-F(ab')2 or anti-mu chain antibodies were unable to activate human non-T lymphocytes, but usually induced a partial inhibition of the Cowan Staph-induced cell proliferation. Non-T cells from 2 patients with CLL did not respond to either Fab or F(ab')2 fragments of anti-Ig antibodies, but were stimulated to proliferate by Cowan Staph. However, the proliferative response of non-T cells from these patients to Cowan Staph was markedly inhibited or abolished by the addition to the cultures of F(ab')2 fragments of anti-Ig antibodies. Antibody preparations to human F(ab')2 or gamma-chain inhibited the response of IgG-bearing leukemic cells, whereas the Cowan Staph-induced proliferation of IgM-bearing leukemic lymphocytes was inhibited by the addition to the cultures of either anti-F(ab')2 or anti-mu chain antibodies. The proliferative response to Cowan Staph or normal non-T cells was also inhibited by the addition to the cultures of human and guinea pig polyclonal IgG, whereas IgG from other species, such as goat, ox, horse, and rabbit, were poorly or not at all inhibitory. On a molar basis, the F(ab')2 preparation from human IgG was as potent an inhibitor as intact IgG molecules, whereas Fc gamma was much less effective in inhibiting the Cowan Staph-induced cell proliferation. A monoclonal IgM, isolated from the serum of a patient with CLL, whose lymphocytes were able to form rosettes with SpA-HRBC and to proliferate in vitro after stimulation with Cowan Staph, also showed a marked inhibitory activity on the Cowan Staph-induced proliferation or normal non-T cells. These data suggest that an interaction between SpA present on the bacterial cell wall and a structure located in the Fab region of sIg, which is shared by sIgM, sIgG, and perhaps also by sIg of other classes, plays an important role in the triggering of B cell proliferation induced by SpA-containing staphylococci.

Surface immunoglobulins are involved in the interaction of protein A with human B cells and in the triggering of B cell proliferation induced by protein A-containing Staphylococcus aureus

The nature of surface components responsible for the reactivity of a subset of human B cells with staphylococcal protein A (SpA) was studied. The ability of normal non-T cells or non-T cells from patients with chronic lymphocytic leukemia (CLL) to form rosettes with human red blood cells coated with SpA (SpA-HRBC) was strongly inhibited or abolished by incubation with F(ab')2 fragments of antibodies against human immunoglobulin (Ig), whereas the incubation with F(ab')2 fragments of antibodies against a non-Ig cell surface antigen, such as beta 2-microglobulin, had no effect on the SpA-rosetting of human lymphocytes. The role of the reaction between surface Ig (sIg) and SpA in the triggering of the proliferative response induced by Staphylococcus aureus bacteria strain Cowan I (Cowan Staph) on normal or leukemic non-T cells was also investigated. A parallelism was observed between the mitogenic activity on normal human non-T cells of Cowan Staph and F(ab')2 fragments of immunosorbent-purified rabbit antibodies to human mu-chain. On the other hand, monovalent Fab fragments of anti-F(ab')2 or anti-mu chain antibodies were unable to activate human non-T lymphocytes, but usually induced a partial inhibition of the Cowan Staph-induced cell proliferation. Non-T cells from 2 patients with CLL did not respond to either Fab or F(ab')2 fragments of anti-Ig antibodies, but were stimulated to proliferate by Cowan Staph. However, the proliferative response of non-T cells from these patients to Cowan Staph was markedly inhibited or abolished by the addition to the cultures of F(ab')2 fragments of anti-Ig antibodies. Antibody preparations to human F(ab')2 or gamma-chain inhibited the response of IgG-bearing leukemic cells, whereas the Cowan Staph-induced proliferation of IgM-bearing leukemic lymphocytes was inhibited by the addition to the cultures of either anti-F(ab')2 or anti-mu chain antibodies. The proliferative response to Cowan Staph or normal non-T cells was also inhibited by the addition to the cultures of human and guinea pig polyclonal IgG, whereas IgG from other species, such as goat, ox, horse, and rabbit, were poorly or not at all inhibitory. On a molar basis, the F(ab')2 preparation from human IgG was as potent an inhibitor as intact IgG molecules, whereas Fc gamma was much less effective in inhibiting the Cowan Staph-induced cell proliferation. A monoclonal IgM, isolated from the serum of a patient with CLL, whose lymphocytes were able to form rosettes with SpA-HRBC and to proliferate in vitro after stimulation with Cowan Staph, also showed a marked inhibitory activity on the Cowan Staph-induced proliferation or normal non-T cells. These data suggest that an interaction between SpA present on the bacterial cell wall and a structure located in the Fab region of sIg, which is shared by sIgM, sIgG, and perhaps also by sIg of other classes, plays an important role in the triggering of B cell proliferation induced by SpA-containing staphylococci.

Bioavailability and pharmacokinetics in man of acipimox, a new antilipolytic and hypolipemic agent

Two separate studies were performed: in the first study for healthy male volunteers received three single oral doses (150, 250 and 400 mg) of 5-methylpyrazine carboxylic acid 4-oxide (acipimox) according to a randomized sequence. Plasma levels of the drug were determined by RIA and urinary excretion by HPLC. In the second trial the effect of food on the drug bioavailability and pharmacokinetics during repeated administration was investigated in six volunteers. The RIA method was adopted to measure plasma and urine levels. Acipimox was rapidly and almost completely absorbed after the three single doses. About 90% of the administered dose was recovered as unchanges drug in urine collected up to 24 h. Peak plasma levels, area under plasma levels curves and urinary excretion were linearly related to the administered dose. The presence of food in the gastro-intestinal tract did not adversely affect the bioavailability of the drug. No significant changes were noted in the rate of elimination after 6 days of treatment with 250 mg t.i.d. Plasma levels determined after the 19th dose were in good agreement with those predicted on the assumption of linear pharmacokinetics and a one-compartment open model, with a half-life of about 2 h.

Radioimmunoassay of glipizide in human plasma

A simple, sensitive radioimmunoassay has been developed for the direct determination of glipizide in human plasma. Antisera raised in rabbits immunized with a glipizide analogue conjugated to bovine serum albumin were highly specific, the two main metabolites, 3, cis-hydroxycyclohexyl derivative and 4,trans-hydroxycyclohexyl derivative, having cross reactivities of 0.73% and 1.66%, respectively. The method can measure amounts as small as 1 ng/ml. The intra- and inter-assay coefficients of variation lay between 2.98-5.79% and 2.35-8.66%, respectively. The mean recovery of glipizide added to plasma was 99-105% over the range 1-500 ng/ml. The method was employed to determine plasma levels in six subjects after administration of a 5 mg tablet of glipizide. The results were in accordance with those found after administration of the same dose of radiolabelled glipizide to two other subjects.

Short- and long-term effects of radiation on T-cell subsets in peripheral blood of patients with Hodgkin's disease

The present study was undertaken to determine the effect of radiotherapy on subpopulations of peripheral blood T cells from patients with Hodgkin's disease. T cell were purified from each specimen, and proportions and absolute numbers of T lymphocytes bearing receptors for the Fc portion of IgG (TG) and for Fc portion of IgM (TM) were enumerated by rosetting T cells with ox red blood cells (ORBC), which had been coated with anti-ORBC rabbit IgG or IgM, respectively. In untreated patients, the percentage of TG cells was significantly increased, and the percentage of TM cells was significantly decreased when compared with control values. In patients examined after radiotherapy, there was a severe depletion of total T lymphocytes. The percent and absolute values of TM cells were also markedly decreased in comparison with those found in either normal controls or untreated patients. In contrast, relative proportions of TG cells were significantly increased in the same treated patients, but the absolute numbers of these cells were essentially unchanged in comparison with those found before radiation therapy. There was a partial and progressive restoration of the number of TM lymphocytes some years after the treatment, but reduced percentages of TM lymphocytes and increased percentages of TG lymphocytes were still found in patients in continuous complete remission for at least five years or more. Similar alterations of the two T-cell subsets were also found in the peripheral blood of a small group of patients treated with radiation for testicular seminoma. These data clearly demonstrate that radiation therapy has a differential effect on identifiable and distinct subsets of cells in the human T-cell class.

Inhibition of lipolysis by nicotinic acid and by acipimox

Acipimox (5-methylpyrazinecarboxylic acid 4-oxide) is a new lipolysis inhibitor that has a distant chemical relationship with nicotinic acid (NA). The tritiated compound (100 mg) is rapidly absorbed, peak plasma radioactivity being reached after 2 hr, with an almost total elimination unchanged in urine. A comparison of th antilipolytic activity of three doses of acipimox and three doses of NA showed acipimox to be 20 times as potent as NA. There was a correlation between intensity and duration of effect for acipimox, but not for NA. Plasma acipimox levels correlated with inhibition of lipolysis. In consideration of the very good subjective tolerability of acipimox at all doses tested, this drug may be suitable for control of lipolysis in hyperlipidemias.

T-cell independence of immunoglobulin synthesis by human peripheral blood lymphocytes stimulated with SpA-containing staphylococci

Unfractionated and T-cell depleted human peripheral blood lymphocytes (PBL) were cultured in vitro in the presence of pokeweed mitogen (PWM) and Staphylococcus aureus strain Cowan I (StaCw). After 7 days of culture, the cells were assayed for cytoplasmic immunoglobulins (Cyto-Ig) by direct staining using fluorescein-labelled F(ab')2 fragments prepared from specific antisera against human IgG F(ab')2. The amount of immunoglobulin of the IgM and IgG class released into the cell-free supernatants was also measured by radioimmunoassay. In unfractionated PBL StaCw, like PWM, was able to induce a significant increase of either the number of Cyto-Ig containing cells for the amount of IgM and IgG secreted into the supernatant. In contrast, the amount of IgM and IgG immunoglobulin released into the supernatant of T-cell depleted suspensions stimulated with PWM was significantly reduced in comparison with that of unfractionated populations, whereas it was unchanged in T-cell depleted vs unfractionated suspensions stimulated with StaCw. The addition of a few T lymphocytes restored the ability of T-cell depleted suspensions to produce Ig in the presence of PWM, whereas despite addition of high numbers of T cells no further augmentation of the Ig production induced by StaCw on T-cell depleted suspensions was observed. Cultures of umbilical cord blood lymphocytes (UCBL) stimulated with PWM did not generate Ig-producing cells, whereas UCBL stimulated with StaCw showed significant production of Ig of both IgM and IgG classes. The results indicate that T lymphocytes are probably not involved either with stimulation or with the suppression of Ig production induced by StaCw.

In vitro production of IgE by human peripheral blood mononuclear cells. II. Cells involved in the spontaneous IgE production in atopic patients

Spontaneous IgE production in vitro was investigated in 7-day cultures of unfractionated mononuclear cells (MNC) and MNC subpopulations from atopic patients. Depletion of either phagocytic or adherent cells decreased the amount of IgE detectable in 7-day culture supernatants, but this decrease was due, at least in part, to a loss of cytophilic IgE. Depletion of immunoglobulin-bearing cells (SIg⁺) reduced significantly but did not abolish the spontaneous IgE production in vitro. On the other hand, depletion of IgM-bearing lymphocytes (SIgM⁺), which virtually abolished the production of immunoglobulins of the IgM class, did not change significantly the spontaneous production of IgE. Similarly, no change in the spontaneous production of IgE was found when lymphocyte suspensions were depleted of complement receptor-bearing cells (CR⁺). In contrast, spontaneous IgE production was significantly increased by depletion of T lymphocytes and this increase did not simply reflect the enrichment for IgE-producing cells caused by the fractionation procedure. No significant change in the spontaneous IgE production was found when small numbers of autologous T lymphocytes were added to B cell fractions, whereas the addition of higher concentrations of autologous T cells induced a marked inhibition of the spontaneous IgE production. On the other hand, the addition in culture of pokeweed mitogen (PWM) resulted in a marked reduction of the spontaneous IgE production by B cells, also in the presence of small concentrations of autologous T lymphocytes. Normal T cells were consistently effective in inducing a partial inhibition of the spontaneous IgE production by B cells from atopic patients, whereas T cells from a noticeable proportion of atopic patients were not. These data suggest that MNC responsible for the spontaneous IgE production in atopic subjects are SIgM- and CR-deficient well-differentiated lymphocytes which probably represent the result of an activation which has occurred in vivo. However, this spontaneous IgE production can still be influenced by in vitro manipulation, such as variations in T–B cell ratios or addition of PWM. The results here reported also indicate that normal T cells are generally more effective than T cells from atopic patients in regulating the activity of spontaneous IgE-producing cells present in the blood of atopic subjects.

In vitro production of IgE by human peripheral blood mononuclear cells. I. Rate of IgE biosynthesis

IgE protein and grass-specific IgE antibodies were detected in the supernatants of 7-day cultures of unstimulated and pokeweed mitogen (PWM) stimulated human blood mononuclear cells from non-atopic and grass pollen-sensitive individuals. Significant amounts of IgE protein were detected in culture supernatants of grass-sensitive individuals and, even at lower levels, in those of non-atopic subjects. In contrast, detectable amounts of grass-specific antibodies were found only in the culture supernatants of grass-sensitive subjects. The mean values of total and grass-specific IgE detected in the supernatants of unstimulated and PWM-stimulated cultures did not differ statistically. Time sequence studies showed that IgE concentrations, measured in the 7-day supernatants, were due to a continuous release from the cells of IgE quantities progressively decreasing up to days 7 or 8. Comparison of the IgE protein and IgE antibody found in the 7-day culture supernatants to those released from initial cell pellets by treatment with acid buffer or freezing and thawing, showed that the IgE detected in 7-day supernatants could result, in part, from the release of cytophilic IgE bound to basophil or other cell types and in part also from the release of preformed lymphocyte cytoplasmic IgE into the supernatant fluids during the course of culture. In most non-atopic subjects and in some grass-sensitive patients the preformed IgE accounted virtually for the total IgE detected in the 7-day culture supernatants. However, the increase of IgE above the levels measured in the initial cell pellets, which was found in most grass-sensitive subjects, clearly reflected newly synthesized IgE. Both cycloheximide and puromycin were capable of reducing significantly the IgE concentration in culture supernatants when it was greater than the amount found in the initial cell pellets. The treatment of cells with mitomycin C was also able to decrease significantly the amount of IgE released in the supernatant after day 3 of culture.

Hyperproduction of IgE and T-cell dysfunction in Hodgkin's disease

Serum IgE levels were evaluated in 119 untreated and 112 treated patients with Hodgkin's disease (HD). 38 of the nonatopic untreated patients showed significantly increased (> 300 IU/ml) IgE concentrations. No relationship could be found between increased IgE levels and depressed lymphocyte response to phytohemagglutinin (PHA) or the imbalance of TM and TG lymphocyte subsets. On the other hand, the mean level of suppressor activity elicitable from cells of untreated HD patients by concanavalin A preincubation did not differ significantly from that of healthy control subjects. In contrast, in treated patients, where there was a significant reduction in the number of circulating T lymphocytes, a further depression of the lymphocyte response to PHA, a more marked disproportion of TM and TG cell subsets and a noticeable fall in IgE concentration was found. These data suggest that increased IgE concentrations seen in untreated patients with HD are unrelated to the T-cell defects. They also suggest that hyperproduction of IgE is probably not invariably a consequence of a suppressor cell deficiency.

Study of some properties of the receptor for IgM on human lymphocytes

Some properties of the receptor for IgM on human lymphocytes have been investigated. It was shown that the interaction of native IgM with the receptor present on T and B lymphocytes is not critical for its detection in the EAM-rosette assay. In fact, high values of EAM-RFC could be found on cell suspensions cultured overnight in either IgM-free or IgM-containing media. In addition, the inhibition of EAM-rosettes by human monoclonal IgM at 37 degrees C was not as effective as at 4 degrees C. Rabbit IgM showed a significantly greater ability to inhibit the binding of antigen-IgM antibody complexes than human IgM. The receptor for IgM was easily removed by handling procedures, the incubation of lymphocytes at 4 degrees C and treatment of the cells with low concentrations of trypsin or pronase. After the enzymatic treatment, a rapid resynthesis occurred, which restored the number of EAM-rosettes formed by T cells and significantly increased the number formed by B cells. The interaction between the receptor and antigen-IgM antibody complexes stopped the spontaneous shedding of the receptor at 4 degrees C. When the incubation of the cells with immune complexes was performed at 37 degrees C, a significantly different behaviour between T cells equipped with receptor for IgM and those possessing receptor for IgG was found. After the binding of EAG to the receptor for IgG, a process of rapid dissociation of rosettes occurred, whereas the incubation with EAM did not induce an irreversible loss of the receptor for IgM.

Different mitogenic activity of soluble and insoluble staphylococcal protein A (SPA)

The response to SPA and Staphylococcus strain Cowan I (StaCw) of highly purified populations of peripheral blood and tonsil human lymphocytes was investigated. Purified T lymphocytes isolated from perpheral blood by E-rosetting were unable to respond in vitro to StaCw. Highly purified B-cell populations from tonsils did not show any proliferative response in the presence of soluble SPA. The addition to highly purified B-cell suspensions from human tonsils of increasing concentrations of autologous T lymphocytes did not induce any increase of thymidine uptake in the presence of StaCw. However, it was able to restore a marked proliferative response of the B-cell cultures to soluble SPA, even though mitomycin-treated T lymphocytes were added. The low response of highly purified peripheral blood T lymphocytes to soluble SPA could be potentiated by the addition of autologous mitomycin-treated B cells, whereas the unresponsiveness of purified T lymphocytes to StaCw was not affected. Mitogenic activity of SPA coupled to Sepharose beads was different from that of soluble SPA and paralleled that of StaCw. These data strongly suggest that insoluble SPA is a T-cell-independent B-cell mitogen in man, whereas soluble SPA, like PWM, exerts its activity on B cells only in the presence of T cells.

Altered proportion of T mu-and T gamma-cell subpopulations in patients with Hodgkin's disease

The ability of peripheral blood lymphocytes from patients with Hodgkin's disease (HD) to form rosettes with ox red blood cells (ORBC) sensitized by anti-ORBC purified rabbit IgM and IgG was investigated. The mean percentage of cells capable of forming rosettes with ORBC coated with IgM (EAIgM-RFC) in the peripheral blood of either untreated or X-ray-treated patients with HD was significantly lower than that of normal individuals. In the same groups of patients with HD the mean percentage of T lymphocytes equipped with receptor for IgG (T gamma lymphocytes), evaluated by a mixed fluorescent rosette assay, was significantly higher than in normal controls. These data suggest that the altered proportion between T mu-and T gamma-cell subpopulations in patients with HD probably represents a disease-related phenomenon.

Receptors for IgM: a feature of subpopulations of both T and B human lymphocytes

Receptors for IgM were detected on peripheral blood and tonsil human lymphocytes by a rosette technique with ox red blood cells (ORBC) coated with anti-ORBC rabbit IgM. It was found that the receptors are very sensitive to handling procedures of cells and to low temperatures. An overnight incubation period at 37 degrees C was the optimal condition for the maximum expression of receptors for IgM, but the use of IgM-free media in these cultures was neither an essential nor favourable factor for an optimal rosette formation, when ORBC heavily coated with rabbit IgM were used. The great majority of chronic lymphocytic leukaemia (CLL) patients presented a high number of EA(IgM)-RFC, either on freshly drawn or cultured lymphocytes. By fractionation procedures of normal peripheral blood and tonsil lymphocytes, it was found that a subpopulation of B cells, like T cells, also posses a lower avidity for IgM than those present on T lymphocytes.

Co-operation between T and B lymphocytes from human tonsils in the response to mitogens and antigens

Purified B lymphocytes obtained from human tonsil cell populations by removing E rosette-forming cells by density sedimentation did not proliferate at three days in response to PHA and Con A, but showed a significant 3H-labelled thymidine incorporation when the PHA response was assessed at day 6 of culture. The 6th-day responses, which was completely abolished by the reduction of T-cell contamination to less than 0-1% by re-rosetting and a second separation, was due in part to a direct activation by PHA of contaminating T cells and in part to a T cell-mediated B-cell response. When purified B cells were stimulated for 3 days by PHA in the presence of an equal number of autologous or homologous mitomycin-treated T lymphocytes a highly significant uptake of 3H-labelled thymidine was demonstrated. The majority of blast cells obtained at day 4 in these cultures were unable to form E rosettes and showed surface immunoglobulin by immunofluorescence stain. This response was markedly decreased by previous treatment of B cells with mitomycin C and it was abolished when B cells were killed by heating at 56degrees C for 1 hr. Purified B lymphocytes from human tonsils did not respond in vitro when cultured for 6 days in the presence of soluble antigens (PPD and Candida). However, a highly significant response to the same antigens could be demonstrated when B cells were cultured in the presence of autologous mitomycin-treated T cells. These models of T-B co-operation could provide an interesting tool for studying the differentiation and antibody production in vitro of human B lymphocytes.

Study of some immunological parameters in untreated patients with Hodgkin's disease

The immunological reactivity of 40 untreated patients with Hodgkin’s disease was studied by some <i>in vitro </i>tests exploring the lymphocyte function, The response of lymphocytes to PHA was markedly depressed in the advanced stages of the disease, but it appeared significantly decreased also in the initial stages when a suboptimal concentration of the stimulant was used to activate the cells in culture. No significant correlation was found between the depressed lymphocyte response to PHA and a particular histologic pattern of the disease, even though patients with lymphocyte predominance and nodular sclerosis usually showed the best responses. The decrease of PHA-stimulability was not dependent on the activity of free serum factors or by the usually high number of phagocytic cells contaminating the standard quantity of lymphocytes in culture. Nor was it due, at least in the initial phases of the disease, to a depletion of circulating cells able to respond to PHA. In fact, the percentage of Ig-bearing lymphocytes in the peripheral blood was usually normal; E rosette-forming cells were present in normal number in the initial stages of the disease and their percentage was markedly decreased only in a very small number of patients with advanced disease. Virtually all the patients with positive delayed-type skin reactions to PPD and Candida, but also many of those without skin reactivity showed a significant <i>in vitro </i>response to the same antigens. The responding capacity in MLC of lymphocytes was not significantly reduced in comparison to that of normal controls; the stimulatory efficacy of the same cells was decreased in some patients but, at group level, did not appear significantly lower of that of normal controls. An increased level of IgE immunoglobulin could be demonstrated in the serum of many patients with HD. The data here reported demonstrate that a functional defect of lymphocytes is a very frequent finding in untreated patients with HD; they also show that of the tests available for the study of lymphocyte function, the PHA-stimulability seems to be the more sensitive and its alteration always precedes the development of T lymphopenia.