Selective triggering of human T and B lymphocytes in vitro by polyclonal mitogens

Ultrastructural studies of leucocytes which form rosettes with homologous erythrocytes in human auto immune haemolytic anaemia

Leucocytes which form rosettes with himologous erythrocytes in auto-immune haemolytic anaemia, infectious mononucleosis and following the stimulation of lymphocyte cultures with PHA have been studied by electron microscopy. The studies showed that the predominant homologous rosette forming cell was lymphocytic and the evidence favoured the conclusion that they were non-immune in nature. This identification does not classify the lymphocyte as thymus or bone marrow derived. Just under half (44%) of the total lymphocytic RFC had perinuclear microfilaments and limited clearing of the plasma of ribosomes close to the cell membrane. These features are consistent with activated T lymphocytes. The remainder of the lymphocytic RFC had no features which allowed their identification as T or B cells. The form of contact between lymphocytic RFC and erythrocyte was mainly of a pointlike nature, with little deformation or invasion of the attached erythrocytes. Monocytes were the only other type of cell encountered with any frequency. Their prime distinguishing feature was the deformation of attached red cells which they caused.

Felty's syndrome. Clinical and serological analysis of 34 cases

Review of 34 cases of Felty's syndrome showed this to be a form of 'super' rheumatoid disease because of the severity of joint disease, the prominence of extra-articular features and the remarkable incidence of infection. The response to splenectomy in these 34 patients was shown by a return towards normal of peripheral blood abnormalities and a decrease in bone marrow granulopoiesis. Although some patients remained free of infection after splenectomy, others have continued to have infections despite the return of white blood cell counts to normal levels. Although splenectomy and subsequent increase in white blood cell levels may be beneficial, our experience suggests that other factors are important in the susceptibility to infection of Felty's syndrome patients. Moreover, we think that splenectomy may have been instrumental in the fatal infection of one of our patients.

Suppression of human T-cell mitogenesis by prostaglandin. Existence of a prostaglandin-producing suppressor cell

Small amounts of PGE inhibit mitogen-induced [3H]thymidine incorporation in human peripheral lymphocytes. The 50% inhibitory concentration is approximately 10(-7) M, and this is reduced to approximately 10(-8) M when endogenous PGE production is blocked. PGE inhibits PHA- and Con A-stimulated cultures much better than PWM cultures, suggesting a differential effect of PGE on T-cell vs. B-cell function. In vitro blockade of PG synthesis results in approximately 50% increase in [3H]thymidine incorporation in PHA cultures. PGE is produced endogenously in PHA cultures by glass adherent suppressor cells.

Immunosuppression after cholecystectomy

The effect on immune functions of cholecystectomy under combined anaesthesia was studied in nine patients. The parameters examined were the leucocyte and differential count, the T-and B-lymphocyte count, and the lymphocyte transformation induced by phytohaemagglutinin, concanavalin A, pokeweed mitogen and purified protein derivative of tuberculoprotein. The anaesthesia and operation decreased the total lymphocyte count in the peripheral blood. No significant change occurred in the proportion or absolute number of E-binding (T) lymphocytes. The proportion of EAC-binding (B) lymphocytes increased, although no change was observed in the lymphocytes with surface immunoglobulin representing another B-cell marker. A statistically significant decrease was found in the lymphocyte response to all the mitogens used both in cultures with isolated lymphocytes and in whole blood. The changes returned to the pre-induction level on the third postoperative day. These finding suggest a transitory decrease of cell-mediated immunity after cholecystectomy.

Mitogenic stimulation of murine spleen cells by brief exposure to Staphylococcus aureus enteroxin B

Staphylococcal enterotoxin B rapidly and firmly attached to external membrane surfaces of C57BL/6 spleen cells and, unless neutralized by specific antitoxin, committed the spleen cells to strong blastogenic responses.

T-cell and B-cell identification in the diagnosis of lymphoproliferative disease. A review

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Differentiation of human lymphocytes by pokeweed mitogen in vitro: studies in normal and in immunodeficient subjects

Immunoglobulin (Ig) synthesis and secretion by peripheral blood lymphocytes activated by pokeweed mitogen (PWM), and by phytohemagglutinin (PHA) was measured in normal individuals and in subjects with primary immunodeficiency. Unstimulated cultures demonstrated stable, low Ig synthesis of all major Ig classes; PWM showed a peak of Ig synthesis at day 5; PHA cultures demonstrated a late peak of ig production at day 9. Three cases of common variable immunodeficiency showed different patterns of data when the percentage of B cells in blood and Ig production in vitro were used as parameters. Two persons with immunodeficiency and thymoma showed decreased Ig production in vitro, and had suppressor cells capable of blocking Ig production by normal lymphocytes in co-cultivation experments.

Lymphocyte response to phytohaemagglutinin before and after radiation therapy in patients with carcinomas of the head and neck

The ability of peripheral blood lymphocytes to respond in vitro to phytohaemagglutinin (PHA) was studied before and after radiation therapy in patients with locally advanced squamous cell carcinomas of head and neck. Patient lymphocyte response to PHA was depressed before therapy and further declined following therapy. The pre-therapy PHA responsiveness was found to be prognostically significant in regard to patient survival.

Functional analysis of two human T-cell subpopulations: help and suppression of B-cell responses by T cells bearing receptors for IgM or IgG

Subpopulations of thymus-derived T lymphocytes bearing receptors for either IgM or IgG molecules were isolated from human peripheral blood. Those with receptors for IgM (T.M) provided help in a cell dose-dependent fashion for the pokeweed mitogen-induced differentiation of B lymphocytes in vitro, whereas cells with receptors for IgG (T.G) did not. T.G cells, on the hand, efficiently suppressed the differentiation and proliferation of B cells in the pokeweed system in the presence of helper T.M cells. This suppressive activity of T.G cells required prior interaction of the T.G cells with immune complexes. The helper activity of T.M cells was relatively radioresistant while the suppressor activity of T.G cells was radiosensitive. The results indicate that helper and suppressor functions of human T lymphocytes in this model system are mediated by different subpopulations of T cells which can be distinguished by their ability to bind IgM or IgG immune complexes, respectively.

Acid esterase in human lymphoid cells and leukaemic blasts: a marker for T lymphocytes

A non-specific acid alpha-naphthyl-acetate esterase activity was investigated in human lymphoid cell populations from tonsils, blood, thymus and in different leukaemias. Four patterns have emerged. (i) The vast majority of T lymphocytes (peripheral blood, tonsils) showed a localized, intense reaction product ("T-like"). (ii) A thymocyte subpopulation expressed faint, localized enzyme activity ("Thy-like) but the majority of thymocytes showed no esterase activity. Some cells from acute lymphoblastic leukaemias with thymocyte surface characteristics had a "Thy-like" appearance. (iii) Most B lymphocytes and cells from chronic lymphocytic leukaemias were esterase negative. No activity was seen in mitogen activated peripheral blood T and B lymphoblasts from peripheral blood and in leukaemic blasts from the common form of childhood acute "lymphoblastic" leukaemia. (iv) Myeloid cells, including peripheral blood monocytes, and blast cells from acute myeloblastic and chronic granulocytic leukaemias showed an intense, diffuse reaction product (M-like). It is concluded that the modified esterase technique is a convenient marker for small mature human T lymphocytes in tissue sections and smears. It may also be helpful in the differential diagnosis of acute lymphoblastic leukaemia with T characteristics, the common form of acute "lymphoblastic" leukaemia and acute myeloblastic leukaemia.

Leucocyte migration inhibitory activity in supernatants of cultured human mono-nuclear cells stimulated with mitogens or C3- and Fc-receptor reactions

We studied whether reactions at the lymphocyte membrane receptors for complement, immunoglobulin or mitogens would induce lymphokine production. Human peripheral blood mono-nuclear cells were stimulated by C3- or Fc-receptor reactions and with phytohaemagglutinin (PHA) or lipopolysaccharide (LPS) and cultured for 3 or 4 days. C3- and Fc-receptor reactions were brought about by rosette formation with red cells coated with human complement or antibody. Culture supernatants were assayed for migration inhibitory activity with human leucocytes by the leucocyte-migration-in-agarose test. On the average, no migration inhibitory activity could be detected in cultures stimulated by C3- or Fc-rosette formation, mean migration indices (MI) being 99-2 and 96-1, respectively. Of the mitogens, PHA induced distinct lymphokine synthesis (mean MI 60-2) while the mean MI with LPS varied from 97-9-69-8, depending on the mitogen preparation used and the conditions of culture. We conclude that PHA and LPS are able to activate human lymphocytes into elaboration of migration inhibitory factors whilst reactions at C3- or Fc-receptors fail to do so.

Characterization of the direct effects of cyclophosphamide on cell-mediated immunological responses

The direct immunosuppressive effects of cyclophosphamide were examined by incubating normal guinea-pig mononuclear cells with activated cyclophosphamide prepared from the serum of separate animals which were treated with cyclophosphamide in vivo. Treated cells were subsequently assayed in a panel of tests of cell-mediated immunity either immediately or following recovery during variable periods of incubation. It was found that cyclophosphamide (1) induces changes in lymphocyte functions which are not due simply to cell death; (2) is markedly antiproliferative in mitogen-induced blastogenesis; (3) depresses migration inhibitory factor production only after a delay of several hours and (4) depresses certain cytotoxicity reactions immediately following treatment, such responses are subsequently normalized when the cells are allowed to recover in culture.

The persistent PHA-responsive population in the mouse thymus. I. Characterization of the population

Using an in vitro culture technique, mouse thymus graft cells were co-cultured with peripheral blood lymphocytes in the presence of phytohaemagglutinin (PHA). The persistent PHA-responsive thymus graft population (Elliott, 1973) was shown to be able to respond to other T-cell mitogens (Con A, pokeweed mitogen, staphylococcal enterotoxin B), but not to E. coli lipopolysaccharide a known B-cell mitogen. The percentage of persistent PHA-responsive cells did not alter during 5 days in culture and was relatively unaffected by either hydrocortisone or anti-lymphocyte serum treatment in vivo. In allogeneic thymus grafts (AKR leads to CBA), persistent PHA-responsive cells could be demonstrated, which were destroyed when incubated with CBA anti thetaAKR serum and complement. When thymus graft cells were allowed to sediment on a 0.2--2 per cent BSA gradient, it was seen that the PHA-responsive population sedimented faster than the bulk of thymus graft cells. Some separation could be obtained on this gradient between the persistent and non-persistent PHA-responsive cell populations.

Inhibition of antigen- and mitogen-induced human lymphocyte proliferation by gold compounds

Gold sodium thiomalate (GST) inhibited in vitro antigen- and mitogen-triggered human lymphocyte DNA synthesis. Inhibition of responsiveness was observed with concentrations of GST equivalent to gold levels found in serum or tissues of patients receiving chrysotherapy, Inhibition was dependent upon the gold ion itself since GST and gold chloride were both inhibitory whereas thiomalic acid was not. Inhibition could not be explained by nonspecific killing of cells or by an alteration in the kinetics of the responses. GST inhibited mitogen-induced proliferation most effectively when present from the initiation of culture and could not inhibit the responsiveness of cells which previously had been activated by concanvalin A. These findings indicated that GST blocked a critical early step in lymphocyte activation. The degree of GST-induced inhibition of proliferation was increased in cultures of cells partially depleted of monocytes. Moreover, inhibition was reversed by supplementation of these cultures with purified monocytes. These observations suggested that GST blocked thymus-derived (T)-lymphocyte activation by interfering with a requisite function of the monocyte population in initiating such responses. Prolonged incubation of peripheral blood mononuclear cells with GST resulted in diminished mitogen responsiveness upon subsequent culture in the absence of gold. The addition of fresh monocytes restored responsiveness to these populations. Furthermore, preincubation of purified monocytes with GST rendered them deficient in their ability to support mitogen-induced T-lymphocyte proliferation on subsequent culture. These observations indicate that the major effect of GST results from interference with the functional capability of the monocyte population.

Antigen specific lymphocyte activity in vitro by peripheral blood leucocytes from Mantoux positive and negative human beings. I. Comparison of quantitative and qualitative differences in the PPD-specific lymphoproliferative response of lymphocytes from the two kinds of donors

Lymphocytes from some PPD (purified protein derivative from tubercle bacillus) skin test negative (Mantoux negative=Mx--) human beings reacted against PPD in the lymphoproliferative assay with a time course and dose response very similar to those of lymphocytes from Mantoux positive (Mx+) individuals. Other Mx-- persons were PPD non-responsive in the lymphoproliferative assay. The PPD response of (immunoglobulin=Ig) Ig anti-Ig column passed lymphocytes (T-cells) from Mx--/LP+ (LP+=lymphoproliferative) persons was significantly reduced whereas the in vitro PPD response of T-lymphocytes from Mx+/LP+ was the same or increased. Purified B-lymphocytes from all kinds of tested individuals did not respond in vitro against PPD. Serological investigations indicated that one of the reasons for the negative skin reaction of individuals whose lymphocytes gave a positive lymphoproliferative response against PPD in vitro, is that such individuals had recirculating PPD of high molecular weight (greater than 900,000) and/or PPD anti-PPD antibody complexes in the serum. These substances could block the PPD-specific T-lymphocytes.

T-and B-lymphocyte chimerism in the marmoset

Marmosets are natural blood chimeras, this condition resulting from the high frequency of fraternal twinning and the consistent development of placental vasular anastomoses between the two embryos. Identification of chimerism by sex-chromosome analysis of cultured blood lymphocytes provided a means of determining the proportion of chimerism among T and B lymphocytes. Peripheral blood lymphocytes were enriched for T or B cells by filtration through a nylon column (yields greater than 95 per cent T-cells) or inactivation of T lymphocytes by treatment with a goat anti-marmoset thymocyte antiserum in the presence of complement (yeilds greater than 95 per cent B cells). Mitogenic stimulation of these separated, enriched cell populations yielded metaphase plates which could be scored for percentage male and female cells. Tests on five different blood chimeras showed the T- and B-lymphocyte chimerism to be the same. Stimulation of blood lymphocytes with cells from another species of marmoset in a mixed lymphocyte culture test revealed the chimeric T-cell response (i.e., host and co-twin cells) to be similar to that obtained with a mitogenic lectin. The demonstration of equivalent T- and B-cell chimerism in these animals suggests derivation of these cells from a common stem cell pool and the response of both T-cell populations to an antigenic stimulus in proportions similar to their percentage chimerism suggests complete immunologic tolerance exists in this species for co-twin histocompatibility antigens.

T-cell regulation of immunoglobulin synthesis and proliferation in pokeweed (Pa-1)-stimulated human lymphocyte cultures

In pokeweed (Pa-1)-stimulated human lymphocyte cultures, T cells are essential for the survival, proliferation, plasma-cell development, and high-rate Ig secretion of B cells. Their effects are T-cell-specific in the sense that B-cell stimulation does not take place in the absence of T cells even when fibroblasts or monocytes are provided. The experimental system is the most effective model for activation of human B lymphocytes so far described. Plasmablast development requires approximately 7 days in culture. In T + B-cell cultures established at 1 X 10(6)/ml (1 X 10(4)/mm2) initial cell density, plasma cells can secrete, on the average, as much as 40-70 pg IgM or IgG per cell per day. When the initial T-cell density is increased well above 1.0 X 10(6)/ml, a T-cell-mediated depression of Ig synthesis becomes predominant. Thus, in the pokeweed model T-cell effects represent a balance of helper and suppressor influences. The study also shows that B cells are heterogeneous. A non-adherent IgG-committed (smIg-?) TONSIL B-cell population seems to be less susceptible to T suppressor effects than normal tonsil B cells. This subset proliferates particularly well and synthesizes large quantities of IgG in the presence of large initial proportions of T cells.

Identification of a subpopulation of lymphocytes in human peripheral blood cytotoxic to autologous fibroblasts

A naturally occurring subpopulation of human peripheral blood lymphocytes is cytotoxic to autologous and/or allogeneic fibroblasts. The autocytotoxic lymphocytes have a receptor for the third component of complement and for aggregated gamma globulin, do not form rosettes with sheep red blood cells, and are not removed by passage through nylon. The autocytotoxic subpopulation is not present in the thymus and tonsils of normal children or in the peripheral blood of individuals with X-linked agammaglobulinemia. Fibroblast absorption experiments demonstrate that the autocytotoxic cells are "sensitized" to antigens expressed on allogeneic fibroblasts in addition to the antigens expressed on autologous cells. Some normal individuals have a second subpopulation of lymphocytes that may "regulate" the autocytotoxic cells. The relevance of these observations to the murine autocytotoxic cells is discussed.

Demonstration of the production of human thyroid-stimulating immunoglobulins (HTSI) by Graves' lymphocytes cultured in vitro with phytohaemagglutinin (PHA)

The lymphocytes from patients with Graves' disease or from healthy subjects have been cultured in vitro either alone or with phytohemagglutinin (PHA). After six days the culture supernatants have been assayed for their human thyroid-stimulating activity by measuring increases in adenosine 3',5' monophosphate (cyclic AMP) in human thyroid slices with which the supernatants have been incubated. Significant levels of human thyroid stimulator activity were found in the culture in which Graves' lymphocytes were cultured with PHA. This activity has been abolished by precipitation of the IgG from the culture supernatant with goat antihuman IgG serum. In contrast, when Graves' lymphocytes were cultured alone, or when control lymphocytes were cultured either alone or with PHA, there was no overall significant production of human thyroid-stimulating immunoglobulin (HTSI). It is concluded that Graves' lymphocytes can be stimulated by PHA to produce HTSI in vitro. Since PHA is known to stimulate only the T lymphocytes, which do not themselves elaborate immunoglobulins as the B lymphocytes do, the above observations indicate a cooperation between T and B lymphocytes in the production of HTSI, at least in this system.

The effects of purified mitogenic proteins (Pa-1 and Pa-2) from pokeweed on human T and B lymphocytes in vitro

Purified proteins (Pa-1 and Pa-2) from pokeweed have been compared with commercial pokeweed mitogen (PWM-G) and other mitogens in their ability to stimulate human lymphocytes. With cultures of T and B cells separated from tonsil lymphocytes, thymidine uptake, blast transformation and immunoglobulin (Ig) synthesis have been measured. IgM and IgG was measured in supernates of stimulated cultures by radioimmunoassay. Pa-1, Pa-2 and PWM-G were found to be potent mitogens for unseparated tonsil lymphocytes or nylon column purified T cells. Pa-2 was found to be active at lower concentrations than Pa-1, and PWM-G was less potent than the purified mitogens. These three mitogens all stimulated unseparated lymphocytes to secrete large quantities of Ig (20-100 mug/ml) during 7 days in culture. With increasing amounts of mitogens severe decreases in immunoglobulin synthesis were observed at day 6 even with doses which were still optimal for stimulation of thymidine uptake at days 3 and 6. With purified B cells (less than 2% T cells) Pa-1 was the best mitogen for thymidine incorporation. However, the secretory response was very variable. In some experiments B cells did not secrete Ig in response to mitogens; in others Pa-1 was clearly more effective at stimulating secretion than Pa-2 or PWM-G and in some experiments B cells were stimulated by all three. In one experiment Pa-1 stimulated prolymphocytic leukaemia cells to blast transformation and the secretion of IgM. It is concluded that Pa-1, Pa-2 and PWM-G are much better activators of Ig synthesis in human cultures than either PHA or LPS and that Pa-1 is the most reliable B-cell stimulant of the three.

Studies on the mitogenic activity of trypsin, pronase and neuraminidase on human peripheral blood lymphocytes

Human peripheral blood lymphocytes were cultured in the presence of protease (trypsin and pronase) and Vibrio choleraneuraminidase. T and B lymphocyte populations were separated and the effect of these enzymes plus phytohaemagglutin or Tuberculin was studied. The results of these experiments show that proteases moderately stimulate spontaneous deoxynucleic acid synthesis of control cells and potentiate the effect of tuberculin on sensitized cells. These enzymes act specifically on B lymphocytes. Neuraminidase also increases spontaneous deoxyribonucleic acid synthesis of control cells and augments significantly the in vitro response to PPD. There is no additive effect of neuraminidase on phytohaemagglutin stimulated cells. Neuraminidase seems to stimulate specifically T lymphocytes. Some possible mechanisms of action of these enzymes are proposed and discussed.

Activation of human B lymphocytes. I. Direct plaque-forming cell assay for the measurement of polyclonal activation and antigenic stimulation of human B lymphocytes

A model for the detection of single cell antibody production by human tonsillar lymphocytes after stimulation with either sheep red blood cells (SRBC) or polyclonal B-cell activators has been described. The culture system is a modified Mishell-Dutton technique with certain critical factors identified. The assay is a sensitive and resproducible hemolysis-in-gel system employing an ultra-thin layer gel technique measuring plaque-forming cells (PFC) against SRBC targets. Several factors essential for optimal responses are described, but the critical feature of the culture system is the use of selected lots of human AB serum supplements which are extensively absorbed with SRBC. This removes a blocking factor present in most human serum which suppresses the B-cell response to SRBC targets after stimulation with either SRBC or several polyclonal B-cell activators. In addition, absorption of serum with SRBC eliminates the presence of artifactual plaques. Background PFC are extremely low and stimulated cultures show significant and reproducible responses. These studies provide a simple, sensitive, and reproducible model for probing the complex events associated with activation of human B lymphocytes.

Synergy between human T and B lymphocytes in their response to phythaemagglutinin and pokeweed mitogen

Human B- and T-lymphocyte preparations were isolated by separating T lymphocytes that formed rosettes with sheep erythrocytes from unrosetted B lymphocytes. Pokeweed mitogen stimulates the proliferation of both B- and T-lymphocyte preparations. In contrast, phytohaemagglutinin stimulates little or no proliferation of purified B lymphocytes although it stimulates the proliferation of T lymphocytes. Lymphoid preparations containing both T and B lymphocytes are more responsive to both mitogens than are either T- or B-lymphocyte preparations. This observation suggested synergy between T and B lymphocytes in the response of unfractionated lymphocytes to mitogens. The basis for this synergy was shown to be the capacity of T lymphocytes to facilitate the proliferation of B lymphocytes cultured with pokeweed mitogen or phytohaemagglutinin. The activity of T lymphocytes is not dependent upon their proliferation or attributable to their release of mitogenic factors. With regard to the clinical evaluation of immune function, our results indicate that the proliferative response of human lymphocytes to phytohaemagglutinin or pokeweed mitogen cannot be directly related to the percentage of T lymphocytes in the lymphoid preparation.

Activation of human lymphocyte subpopulations by rabbit anti-human beta2-microglobulin and by lipopolysaccharide

Rabbit anti-human beta2-microglobulin (anti-beta2m) was found to increase DNA synthesis in peripheral blood lymphocytes (PBLs) and in cells from abdominal lymph nodes, spleen, tonsil, adenoid, appendix, and bone marrow. The response to anti-beta2m was highest in cells originating from abdominal lymph node, appendix, and spleen. These organs were shown to contain a high proportion of surface-Ig-positive cells. No response to anti-beta2m was seen in thymus cells or in B-cell-depleted lymphocyte populations. Lipopolysaccharide (LPS) increased DNA synthesis in spleen cells, bone marrow cells, tonsil cells, and, sometimes, in cells from abdominal lymph nodes but weakly or not at all in PBLs. To study whether anti-beta2m and LPS activated the same subpopulation of lymphocytes, cultures were exposed to both mitogens in various concentrations. The effect on DNA synthesis in spleen cells was almost additive. This may indicate that these two polyclonal B-cell activators (PBAs) stimulate mainly distinct subsets of B cells in spleen. On the other hand, these two mitogens have a synergistic effect on DNA synthesis in PBLs. Since anti-beta2m is the first described selective B-cell mitogen activating human PBLs, it might be of clinical importance in the functional characterization of lymphocyte subpopulations.

Demonstration of the inhibitory effect of human alpha-fetoprotein on in vitro transformation of human lymphocytes

We have studied the effects of human alpha-fetoprotein (HAFP), isolated from the serum and ascitic fluid of a hepatoma-bearing patient, on the in vitro transformation of human peripheral blood lymphocytes by a variety of mitogenic stimuli. At a concentration of 2.5 mg/ml, HAFP inhibited the lymphocyte response to phytohemagglutinin, concanavalin A, and rabbit anti-human thymocyte serum, but failed to inhibit the response to pokeweed mitogen. HAFP was able to inhibit the one-way mixed lymphocyte culture at concentrations of 250-500 mug/ml, but failed to inhibit at 100 mug/ml. Exposure of lymphocytes to 2.2 mg/ml of HAFP for 18 hr did not result in significant lymphocytotoxicity, and such cells washed free of HAFP were fully capable of participating in the mixed lymphocyte culture. HAFP did not inhibit lymphocyte E-rosette formation. Fetal HAFP was more effective in inhibiting human lymphocyte responses than hepatoma HAFP. These experiments support the suggestion that HAFP plays an important immunoregulatory role during fetal development, possibly through the suppression of thymus-derived lymphocyte responses to antigenic stimuli; they also suggest that there are important differences in the biological properties of hepatoma and fetal HAFP.

SRBC rosette formation as a human T lymphocyte marker

This paper describes a technique utilizing rosette formation with sheep red blood cells as a human T lymphocyte marker, and separation of T cells by rosette sedimentation.

Effects of concanavalin A and a succinylated derivative on lymphocyte proliferation and cyclic nucleotide levels

To better define cell surface-related changes involved in lymphocyte activation, we studied native concanavalin A (Con A) and succinylated concanavalin A (Suc-Con A) for their effects on proliferation and cyclic nucleotide levels of human peripheral blood lymphocytes. At optimal mitogenic concentrations, the two forms of Con A induce equivalent proliferation; however, the mitogenic activity of Con A progressively decreases above 50 mug/ml. In contrast, the mitogenic activity of Suc-Con A is not decreased even at 250 mug/ml.

Modification of the response of human T lymphocytes to phytomitogens by cocultivation with unresponsive non-T leukocytes

Experiments were conducted to ascertain to what extent the mitogen response of human peripheral T cells is influenced by contaminated, nonresponding leukocytes. T- and B-lymphocyte preparations, extensively depleted of monocytes, exhibited extremely poor responses to pokeweed mitogen and concanavalin A compared with the original unfractionated cell population. A strongly reduced phytohemagglutinin response was noted in the B-cell but not in the T-cell fraction. Mixtures of cell preparations enriched in T or B cells yielded stimulations higher than expected. Mitomycin-C-treated T-cell preparations mixed with untreated preparations enriched in B cells gave slightly higher responses than expected. However, highly enhanced responses were observed when untreated T cells were mixed with mitomycin-treated cell suspensions enriched in B cells. A similar enhancing effect was noted when mitomycin-treated cell suspensions enriched in adherent cells were added. It is concluded that the mitogen reactivity of T cells, on a cell-for-cell basis, may be enhanced tenfold or more by cocultivation with unresponsive non-T leukocytes. A reduced mitogen reactivity of peripheral lymphoid cells from patients with various types of disease may thus either reflect a decreased proportion of responsive lymphocytes or unresponsive non-T lymphocytes capable of enhancing mitogen reactivity, or both.

A characterization of human tonsillar lymphocytes after separation from other tonsillar cells in an isokinetic gradient of ficoll in tissue culture medium

Purified human tonsillar lymphocytes responded less to mitogentic stimulation than did unseparated tonsillar cells. Their response to mitogens was restored when they were combined with cells from all other gradient fractions. We interpret our data as evidence that the majority of tonsillar lymphocytes require the presence of more rapidly sedimenting cells for a maximum response to the tested mitogens. The purified tonsillar lymphoyctes were 47.0% lymphocytes that have detectable surface immunoglobulin and 29.9% lumphocytes that form rosettes with sheep red blood cells. The predominant cell surface immunoglobulin was IgM. Digestion of the tonsil with trypsin yielded tenfold more plasma cells, more vialbe cells, and a larger proportion of blasts, histiocytes, and binucleated cells than were obtained by mechanical dissociation of the tissue.

Immunosuppression in the treatment of inflammatory bowel disease. II. The effects of azathioprine on lymphoid cell populations in a double blind trial in ulcerative colitis

Blood lymphocytes and rectal plasma cells have been studied in patients with ulcerative colitis taking part in a double-blind trial of treatment with azathioprine. Treatment for 1 year resulted in a modest fall in blood lymphocyte count, with little change in neutrophils or platelets. There was no major change in the proportions of circulating T and B lymphocytes, suggesting that the number of such cells per millilitre of blood fell in proportion to the change in lymphocyte count. The number of plasma cells in the rectal lamina propria was reduced to a mean less than half that of the control patient group. Blood K-cell cytotoxic activity fell at least 25-fold after 1 year's treatment. PHA-induced cytotoxicity was also reduced, but less consistently. Reduced K-cell activity is interpreted as reflecting depletion of effector cells from the circulation. The fall in lymphocyte count, K-cell activity and gut plasma cells was slow, indicating continuous inhibition of lymphopoiesis or differentiation throughout the trial period. Thus, azathioprine has some immunosuppressive effects which develop only after prolonged treatment. The clinical results of the trial did not show a major beneficial effect of azathioprine in the treatment of ulcerative colitis, nor were there clear correlations between the results of lymphocyte assays and clinical response in individual patients.

Activation of purified human T cells by mitogens: diminished mitogen-induced deoxyribonucleic acid synthesis in human T cells compared with autologous peripheral blood lymphocytes

Human thymus-derived (T) cells were isolated from peripheral blood after rosette formation with neuraminidase-treated sheep erythrocytes (SRBC). After separation on Ficoll-hypaque, SRBC were removed from T cells by treatment with tris(hydroxymethyl)aminomethane-NH4Cl. Human T cells and autologous peripheral blood lymphocytes (PBL) were then incubated with phytohemagglutinin, concanavalin A, or pokeweed mitogen. Human T cells, in the absence of other cell types, responded with less deoxyribonucleic acid (DNA) synthesis (measured by uptake of [3H]thymidine) than equal numbers of autologous PBL. Further experimentation established that, compared with autologous PBL, the diminished capacity of human T cells to be activated by mitogens was due neither to differences in the mitogen dose-response relationship nor to the time of peak DNA synthesis of T cells or autologous PBL. Fragments or components of SRBC were not detected on human T cells, and treatment of the T cell-SRBC mixture with tris(hydroxymethyl)aminomethane-NH4Cl did not contribute to the results. Increased cell density or a period of preculture before addition of mitogen also did not influence the degree of decreased DNA synthesis in human T cells compared with the response of autologous PBL incubated with the same mitogens. When mixed with the cells remaining at the Ficoll-media interface, purified human T cells did not suppress the mitogenic response of this cell mixture to PHA or concanavalin A. The data indicated that human T cells, in the absence of other cell types, were activated by mitogens to a lesser degree than autologous PBL. Furthermore, T cells responded with DNA synthesis after direct T cell-mitogen interaction.

Rabbit lymphoid cells. I. T-cell mitogens, cell volume and adherence properties as probes for cellular heterogeneity

Thymus-derived cell populations were characterized by sedimentation velocity in the Earth's gravitational field, by adherence properties, and in terms of the thymus-specific antigen RTLA. T cells, responding to mitogens, could be shown to be a subpopulation of RTLA-bearing cells and to have a relatively large volume. The size distribution of mitogen-responsive cells from different individuals showed some variation, but in general large spleen cells took up less thymidine per 10(6) cells than did large cells from other lymphoid organs. Upon stimulation with concanavalin A (con A) small popliteal lymph node cells took up more thymidine per 10(6) cells than did small thymus cells. The corresponding small cells of mesenteric lymph node and spleen took up intermediate quantities of thymidine. Thymus-derived cells that were resistant to complement-mediated cell kill with RTLA antiserum showed greater responsiveness to con A than did the original cell preparations. Non-adherent cells incorporated more thymidine when stimulated with phytohaemagglutinin (PHA) than when they were stimulated with con A. Lightly adherent cells were relatively more responsive to con A stimulation and firmly adherent cells were less responsive to both. The findings were discussed in terms of the density of RTLA on the membranes of T cells. In adherence and in sedimentation velocity fractionation, the relative yield of nucleated cells always exceeded the yield of PHA- and con A-responsive cells. The differential separation of mitogen responsive and of co-operating cells were considered as a possible cause of this deficit.

A population of human lymphocytes staining for esterases

A population of lymphocytes is found to stain positively for esterases. The positively staining lymphocytes are more predominant among T than B lymphocytes and are significantly increased on stimulation with PHA. Treatment with cholinestrase inhibitors reduces their number significantly.

Enumeration of polyclonal mitogen-responsive cells in different lymphoid tissues of the mouse

The relative number of cells capable of responding to Con A, PHA and LPS in the spleen, blood, lymph node and Peyer's patches of CBA mice has been quantified by means of a cytological analysis technique. No difference has been found between Con A- and PHA-responsive cells in spleen and lymph node. The lymphoid tissues of T cell-deprived mice have a reduced content of PHA responsive cells, but LPS responsiveness is within normal limits. Pretreatment of peripheral lymphocyte populations with high concentrations of anti-O antiserum and complement abolishes the response of the treated cells to PHA, but not to LPS, whereas similar treatment with a cytotoxic anti-immunoglobulin serum, which has no effect on PHA-responsive cells, only partially reduces the response to LPS. The results for mitogen responsiveness are discussed with reference to other methods of quantifying T and B cells using cell-surface markers.

Lymphocyte activation. VIII. The application of a whole blood test to the quantitative analysis of PHA responsive T cells

In diluted blood predominantly T cells responded to purified PHA (pure leucoagglutinin Wellcome). Red cells and non-T mononuclear cells increased PHA responsiveness of T cells at concentrations present in the peripheral blood. Addition of polymorphonuclear leucocytes was a very slight further advantage. The incorporation of [3H] thymidine reflected the numbers of T cells in culture, although not perfectly linearly, since counts increased when more T cells were added to the cultures. It was therefore concluded that in cultures of diluted whole blood non-specific amplification mechanisms were provided and responses reflected the performance of stimulated T lymphocytes. Since the method is simple and the number of technical variables is relatively small, it is possible to establish a "normal" range of PHA responsiveness expressed in absolute counts per minute, and thus directly compare results from different laboratories.

In vivo and in vitro selection of mitogen responsive lymphocytes in patients with chronic lymphocytic leukemia

The in vitro mitogen response of blood lymphoid cells from patients with chronic lymphocytic leukemia was observed to be low compared to lymphocytes from healthy subjects. However, highly responsive cells could be separated from the blood of such patients by a buoyant density centrifugation technique and such reactive cells were found to be enriched by treating the patients with chemotherapy or splenic irradiation.

Isoprinosine augmentation of phytohemagglutinin-induced lymphocyte proliferation

The need for agents designed to modify immune response in the treatment of patients with viral infection, immunodeficiency, or cancer prompted the present study on the mechanisms of action of isoprinosine, a compound developed for antiviral use and whose therapeutic activity may involve the immune system. The effect of isoprinosine on in vitro proliferation of human peripheral blood lymphocytes stimulated by phytohemagglutinin (PHA) and on lymphocyte levels of cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate was analyzed. Over a concentration range from 0.2 to 250 mug/ml, isoprinosine augmented PHA-induced proliferation; maximal stimulation was observed between 25 to 50 mug/ml. Isoprinosine in the absence of PHA had no effect on proliferation. The relative lack of effect of isoprinosine during a 90-min exposure and the lack of effect on lymphocyte cyclic nucleotide levels indicate that isoprinosine potentiates the PHA response by a mechanism different than a number of hormonal agents and such immunopotentiators as levamisole, polyadenylic-acid, and endotoxin. Further evaluation of isoprinosine as an immunopotentiator is indicated.