In vitro activation of mouse lymphocytes in serum-free medium: effect of T and B cell mitogens on proliferation and antibody synthesis

Immune-enhancement effects of Angelica gigas Nakai extracts via MAPK/NF-ƙB signaling pathways in cyclophosphamide-induced immunosuppressed mice

This study investigated the immune-enhancement effects of Angelica gigas Nakai extract (ANE) and its yeast-fermented extract (FAN) in cyclophosphamide (CPP)-induced immunosuppressed mice. Angelica gigas Nakai (AGN) increased the protein level of inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO) and immune-related cytokines in mouse splenocytes. AGN also restored CPP-induced suppression of NK cell activity and splenocyte proliferation. Furthermore, AGN activated the ERK and p38 MAPK/NF-κB signaling pathways in mouse splenocytes via phosphorylation of signaling molecules. These findings indicate that upregulation of cytokines and enzymes may be closely associated with the MAPK/NF-κB signaling pathways. In conclusion, AGN can restore CPP-induced immunosuppression in mice, although there was no significant difference in the immune-enhancing effect between ANE and FAN. It is suggested that AGN might have the potential to enhance immunity as an immunostimulant under immunosuppressed conditions. Therefore, it could be used as an effective agent or a dietary supplement for improving immunity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01281-6.

Stimulatory effect of Holy basil and Thai basil on mouse spleen cell proliferation

Study was conducted on mouse spleen cells, cultured and incubated in-vitro with Holy basil and Thai basil, to observe their effect on proliferation. Four dilutions, namely 1:1, 1:5, 1:25, and 1:125, for both Holy basil and Thai Basil were used separately, in presence and absence of mitogen, Concanavalin A (Con A) to stimulate the T cells. Cell proliferation was monitored by 3 H- thymidine radioisotope incorporation. Spleen cells (macrophages, B and T cells) showed significantly more proliferation at 1:1 dilution than control (cells with no factor), incubated with Holy basil (in assay without Con A). Spleen T cells, however, did not show any significance in proliferation at same dilution, 1:1, with Holy basil with Con A. All other dilutions (with or without Con A), for either Holy basil or Thai basil, did not show any significant changes in proliferation when compared to control.

How bacterial carbohydrates influence the adaptive immune system

The capsular polysaccharides (CPSs) of most pathogenic bacteria are T cell-independent antigens whose conjugation to carrier proteins evokes a carbohydrate-specific response eliciting T cell help. However, certain bacterial CPSs, known as zwitterionic polysaccharides (ZPSs), activate the adaptive immune system through processing by antigen-presenting cells and presentation by the major histocompatibility complex class II pathway to CD4(+) T cells. This discovery was the first mechanistic insight into how carbohydrates-a class of biological molecules previously thought to be T cell independent-can in fact activate T cells. Through their ability to activate CD4(+) T cells, ZPSs direct the cellular and physical maturation of the developing immune system. In this review, we explore the still-enigmatic relations between CPSs and the adaptive immune machinery at the cellular and molecular levels, and we discuss how new insights into the biological impact of ZPSs expand our concepts of the role of carbohydrates in microbial interactions with the adaptive immune system.

Type I Streptococcus pneumoniae carbohydrate utilizes a nitric oxide and MHC II-dependent pathway for antigen presentation

Some pathogenic bacteria form thick capsules that both block immune responses through inhibition of complement deposition and phagocytosis and stimulate a weak response resulting from a lack of T-cell involvement. Contrary to this model, capsular polysaccharides from 23 serotypes of Streptococcus pneumoniae have been successfully used in a multivalent vaccine in the absence of a carrier protein. Furthermore, type I pneumococcal polysaccharide (Sp1) has been shown to activate T cells in vivo and in vitro via an uncharacterized mechanism. In the present report, we demonstrate that Sp1 utilizes the major histocompatibility complex (MHC) class II pathway in antigen-presenting cells (APCs) for processing and presentation. APCs internalize and process Sp1 through a nitric oxide-dependent mechanism and, once inside the cell, it associates with MHC II proteins in an H-2M-dependent manner that leads to in vivo T-cell activation. These results establish that Sp1 activates T cells which can lead to abscess formation in mice through an H-2M-dependent polysaccharide antigen presentation pathway in APCs, potentially contributing to pneumococcal polysaccharide vaccine efficacy through the recruitment of T-cell help.

Poly A:U-induced secretion of T-lymphocyte helper factors

In vitro exposure of mouse thymocytes to complexes of polyadenylic:polyuridylic acid (poly A:U) effected, within 6 h, the release of soluble factor(s) capable of nonspecifically enhancing IgM and IgG plaque-forming cells (PFCs) in in vitro primary and secondary spleen cell responses to burro erythrocytes. Poly A:U stimulation was, most likely, polyclonal, since production of soluble factor(s) occurred in the absence of antigen and in serum-free culture media. Poly A:U-induced soluble factor(s) were not capable of substituting for T cells but were dependent on T cells for the expression of PFC enhancement. These data support the hypothesis that the mechanism of poly A:U's adjuvant action is polyclonal stimulation of T cells, causing early induction and release of nonspecific, soluble PFC-enhancing factor(s).

Teichoic acids and related cell-wall glycopolymers in Gram-positive physiology and host interactions

Most Gram-positive bacteria incorporate membrane- or peptidoglycan-attached carbohydrate-based polymers into their cell envelopes. Such cell-wall glycopolymers (CWGs) often have highly variable structures and have crucial roles in protecting, connecting and controlling the major envelope constituents. Further important roles of CWGs in host-cell adhesion, inflammation and immune activation have also been described in recent years. Identifying and harnessing highly conserved or species-specific structural features of CWGs offers excellent opportunities for developing new antibiotics, vaccines and diagnostics for use in the fight against severe infectious diseases, such as sepsis, pneumonia, anthrax and tuberculosis.

The love-hate relationship between bacterial polysaccharides and the host immune system

This article explores the fascinating relationship between the mammalian immune system and the bacteria that are present in the mammalian gut. Every human is an ecosystem that hosts 10(13)-10(14) bacteria. We review the evidence that immunomodulatory molecules produced by commensal bacteria in the gut have a beneficial influence on the development of certain immune responses, through eliciting the clonal expansion of CD4(+) T-cell populations. This process seems to contribute to the overall health of the host by offering protection against various diseases and might provide supporting evidence at a molecular level for the 'hygiene hypothesis' of allergic immune disorders.

Absence of lipopolysaccharide high-dose paralysis in B-cell responses: implications for the one-signal theory

Over 20 years ago, Coutinho and Möller reported that high concentrations of LPS were paralytic for the development of antibody secreting cells (ASC). This data was used to explain bell-shaped dose-response curves observed for antihapten antibody formation in response to haptenated LPS. In turn, this bell curve was used to formulate the one-signal model of B cell activation, which argued that antigen signalling was generally unimportant to B cell responses. The present paper re-examines LPS dose-response curves and finds results that do not support the view that high doses of LPS inhibit B cell differentiation to ASC. If high-dose paralysis is not an attribute of LPS stimulation, then the bell-shaped dose curve for hapten-specific ASC originally observed by Coutinho and Möller required an alternative explanation. Through the use of haptenated Ficoll, it was possible to show that the generation of LPS-induced antitrinitrophenol ASC could be inhibited by antigen presented on an inert substrate. Thus, the transmission of surface Ig-mediated (antigen) signals at higher concentrations can explain the antihapten bell-shaped dose curves, in contradiction to the conclusions of the one-signal model.

Regulation of ERK2 dephosphorylation in G1-stimulated rat T lymphoblasts

Rat T lymphoblasts arrested in the G1 phase of the cell cycle by interleukin-2 (IL-2) deprivation can be forced to proceed to the S phase when they are stimulated with IL-2 or the phorbol ester phorbol 12,13-dibutyrate (PDBu). When PDBu is used as a stimulus, extracellular regulated kinase 2 (ERK2) is activated by threonine and tyrosine phosphorylation by the dual-specificity kinase MEK. Here we have studied the regulation of ERK2 dephosphorylation as a mechanism for inactivation of this kinase. In vivo inhibition of ERK2 dephosphorylation observed after preincubation with translation or transcription inhibitors (cycloheximide or actinomycin, respectively) indicates the involvement of at least one inducible phosphatase, the best candidate for which is the dual-specificity phosphatase PAC-1. Other noninducible phosphatases must act as well, however, because sodium orthovanadate is a more effective dephosphorylation blocker than cycloheximide. In addition, the okadaic acid effect in ERK2 dephosphorylation indicates that Ser/Thr phosphatases are also involved, directly and/or indirectly.

Raf-1 and ERK2 kinases are required for phorbol 12,13-dibutyrate-stimulated proliferation of rat lymphoblasts. ERK2 activation precedes Raf-1 hyperphosphorylation

Rat lymphoblasts are arrested in the G1 phase of the cell cycle and can be promoted to proceed up to the S phase, when they are stimulated by phorbol ester. In this work, we have studied some details of the phorbol 12,13-dibutyrate (PBu2)-stimulated proliferation. We show that in response to PBu2 at least four different protein kinase C (PKC) isoforms translocate to the membrane. A specific PKC zeta antibody recognizes two bands of 75 and 82 kDa. These two activities are separated using a Mono Q chromatography and we show that p75 is the classical PKC zeta isoform, while p82 might be a related isoform which is PBu2 sensitive. Our data show that there is a correlation between the ability of PBu2 to promote mitogenesis and to activate ERK2 kinase, suggesting that ERK2 kinase might be the limiting step of the process. We also show that ERK kinase activation precedes Raf-1 kinase hyperphosphorylation, suggesting that Raf-1 kinase activation is not required for ERK kinase activation. This idea was checked using a Raf-1 kinase antisense (AS) oligonucleotide. The results obtained with the Raf-1 AS oligonucleotide indicate that this serine/threonine kinase is dispensable for ERK kinase activation, but needed for the PBu2 mitogenic signaling even as late as 7 h after the delivery of the signal.

Serum-free cell culture

Cell culture is one important tool when studying cellular functions and molecular biology. It is also a basic method in most virological investigations. Serum has been an obligatory component in most cell culture media. During the last decades serum-free, chemically defined media have been developed, that are supplemented with a number of substances with specific cellular activities. The main developments of defined media are presented. Examples are given of investigations with different cell types.

Lectins and antibodies as tools for studying cellular interactions

Specific interactions between multiple cell types are critical for a variety of processes central to the development, homeostasis and immune defense of multicellular organisms. Studies designed to elucidate how cells communicate through physical encounters have exploited exogenously supplied factors to bypass intrinsic recognition mechanisms and facilitate cellular conjugation. In this review, we compare the relatively nonspecific agglutinating properties of lectins and the selective cell targeting capabilities of antibodies and bispecific antibody constructs for studying cell-cell interactions in immunobiology. In addition, we discuss a novel system for inducing cellular interactions which closely resembles native receptor-mediated conjugation. In this system, surrogate receptors promote specific cell-cell interactions without hindering endogenous receptor-ligand interactions at the cell-cell interface which may be important in mediating physiologic cellular responses.

Iron and transferrin uptake by phytohemagglutinin-stimulated human peripheral blood lymphocytes

Iron (Fe) and transferrin (TF) uptake by human peripheral blood lymphocytes stimulated in vitro with phytohemagglutinin was measured. Pulses of 59FeTF or 125I-TF were added to the cultures either at time 0 or 8 hr before the end of a 72-hr incubation. In time-course experiments, peak iron and transferrin uptake coincided with the peak of tritiated thymidine uptake taken as a measure of cellular activation. Iron, but not transferrin, was accumulated by the cells. Non-linear relationships existed between both iron and transferrin uptake and the degree of activation. Both rose markedly above basal levels only at a level of activation at least 50% of the maximum observed. The results suggest that although iron utilization is related to cellular activity, the uptake mechanism is only activated when an increased iron metabolism has exhausted internal stores.

Production and assay of ovine T cell growth factor by concanavalin A stimulated peripheral blood leukocytes

Conditions for the production and assay of ovine T cell growth factor (TCGF) activity were evaluated. Peripheral blood leukocytes were stimulated with concanavalin A (Con A) in the presence of 2% autologous serum or serum-free media. Supernatants were harvested after 30 hr and concentrated for further characterization. A 28 hr proliferation assay with 2.5 X 10(4) 24 hr Con A blasts per well was optimal for detection of TCGF. Peak TCGF activity occurred with a 30-37 KD molecular weight fraction. Production and assay of TCGF were performed under autologous conditions to reduce background stimulation which occurred when fetal bovine serum was present. This methodology required no cell lines or inbred animals and should be adaptable to the study of immunostimulatory molecules of other outbred species.

Application of a serum-free medium in the growth and differentiation of human peripheral blood lymphocytes

To eliminate variability due to nonspecific stimulation or inhibition by different lots of fetal bovine serum, the activation of human peripheral blood mononuclear cells in a modification of Iscove's medium (medium C-IMDM) was compared with the routinely used Roswell Park Memorial Institute (RPMI)-1640 medium containing 15% fetal bovine serum. Stimulation of peripheral blood mononuclear cells was enhanced and occurred at lower mitogen concentrations in C-IMDM compared with cells grown in RPMI-1640 supplemented with fetal bovine serum. Maximum incorporation of [3H]thymidine following stimulation by concanavalin A, phytohemagglutinin, and pokeweed mitogen was more than twice the peak values obtained in RPMI-1640 supplemented with fetal bovine serum. Concentrations of concanavalin A and phytohemagglutinin required for maximum stimulation were 0.5 and 15 micrograms/ml, and 0.3 and 1.0 micrograms/ml . 5 X 10(5) cells in C-IMDM and RPMI-1640, respectively. Cells grown in C-IMDM responded to lower concentrations of pokeweed mitogen and optimal growth in the serum-free medium required 0.4 micrograms/ml . 5 X 10(5) cells. The stimulation of immunoglobulin-producing cells in C-IMDM was enhanced and occurred at lower concentrations of pokeweed mitogen. Less variability of growth (i.e., incorporation of [3H]thymidine) and immunoglobulin synthesis occurred in peripheral blood mononuclear cells cultured in different preparations of C-IMDM than that reported for cells cultured in RPMI-1640 supplemented with different lots or batches of fetal bovine serum. These data suggest that C-IMDM may be an alternative to media supplemented with fetal bovine serum.

Functional analysis of pokeweed mitogen-dependent cell interactions in murine spleen cells. I. Lack of B-cell mitogenicity and low frequency of effector helper T cells

The nature of lymphocyte responses on addition of pokeweed mitogen (PWM) to normal murine spleen cells was studied in low cell density cultures. PWM, over a wide range of concentrations, stimulated proliferation in a set of cells roughly 10-fold smaller than the lymphocyte populations responding to either concanavalin A or lipopolysaccharide. PWM also induced a relatively small number of B lymphocytes in these cultures to mature to Ig-secreting plaque-forming cells (PFC). Proliferative and PFC responses were completely abrogated by T-cell removal from normal spleen cell cultures. Moreover, cell mixture and irradiation experiments demonstrated that B lymphocytes do not proliferate in response to PWM, even in the presence of an excess of normal T cells, suggesting that PFC development results from terminal maturation without proliferation. Finally, parallel titrations of cloned helper cells, normal splenic T cells or T-cell blasts induced by PWM showed that the poor B-lymphocyte responses in normal spleen cell cultures is due to the very low frequency of competent helper cells in these populations. PWM, however, was competent to activate and expand this set of helper lymphocytes in primary cultures.

Secretion of IgG1 induction factor by T cell clones and hybridomas

IgG1 induction factor elevates the IgG1 response induced by lipopolysaccharide and suppresses the lipopolysaccharide-induced IgG3 and IgG2b responses in cultures of mouse spleen cells. We have developed new T cell lines secreting this factor by cloning mixed lymphocyte culture populations. Using supernatants of one of these T cell lines it was found that the assay is quantitative, reproducible and accurate, both when induction of IgG1 as well as reduction of IgG3 and IgG2b were measured. Using this analysis, different conditions to induce maximal production of the factor were tested. The cell line was thereafter used as fusion partner with a T cell lymphoma. The hybrids were selected in the presence of T cell growth factor and all of them secreted IgG1 induction factor.

Activity of acid phosphatase in resting and mitogen-stimulated human peripheral blood lymphocytes

Activity of acid phosphatase was found to be higher in T than in non-T cells of human peripheral blood lymphocytes. The T cell mitogen PHA induced an increase in the magnitude of acid phosphatase activity, while the B cell mitogen LPS was not able to produce any effect on acid phosphatase activity. Acid phosphatase activity in lymphocytes correlated with their spontaneous proliferative activity.

A common sequence of calcium and pH signals in the mitogenic stimulation of eukaryotic cells

When normal quiescent (G0) cells are stimulated by mitogens to enter the cell cycle, the metabolic derepression which occurs is similar in a variety of cells. The mechanisms initiating these responses and their relationship to subsequent progression through G1 to DNA synthesis in S phase, however, are generally undefined. The clearest evidence has been obtained in sea urchin eggs, where fertilization by sperm causes a rapid, transient increase in the concentration of free cytoplasmic Ca2+ [(Ca]i), followed by a sustained increase in cytoplasmic pH (pHi). It has been demonstrated clearly that these ionic responses are obligatory for progression to DNA synthesis by the normal pathway after fertilization, although the Ca2+ signal can be bypassed by parthenogenetic agents which elevate directly pHi (for example, NH+4 ions). These observations raise the questions of whether other eukaryotic cells show the same sequence of ionic responses when stimulated by mitogens and whether such signals are an obligatory component of their mitogenic pathways. We show here that a common sequence of [Ca]i and pHi responses occurs in both quiescent mouse thymocytes and Swiss 3T3 fibroblasts stimulated by appropriate mitogens. Furthermore, 'opportunistic' mitogens (those that do not act on the cells in vivo, such as concanavalin A (Con A), the Ca2+ ionophore A23187 and 12-o-tetradecanoyl phorbol 13-acetate CTPA] that are mitogenic for both mouse thymocytes and 3T3 fibroblast, each produce characteristic ionic responses that are the same in both types of cell.

Ontogeny of T-cell mitogen response in Lewis rats: I. Culture conditions and developmental patterns

Spleen and thymus cells from female Lewis rats 2 to 220 days old were cultured with phytohemagglutinin (PHA) or Concanavalin A (Con A). The optimal dose of Con A for mitogenesis ranged from 1 microgram/ml for suckling rats to 125 micrograms/ml for adult rats. Thymus cells differed from spleen cells in that they required 72 hours for maximum thymidine incorporation; whereas spleen cells attained maximum incorporation within 48 hours. Thymidine uptake in unstimulated spleen cell cultures was high in the neonate and decreased with age. Maximum splenic cell responses to Con A increased from very low levels in the 2-day old to adult levels by 3 weeks coincident with weaning. Maximum PHA responses of splenocytes matured more slowly, reaching adult levels by 8 weeks. Thymus cell responses to Con A and PHA were mature from birth.

In vitro viability of lymphoid cells from lines of mice genetically selected for high or low responsiveness to phytohemagglutinin

The kinetics of viability of lymph node and spleen cells of mice genetically selected for "high" or "low" in vitro lymphocyte responsiveness to PHA were studied in PHA or PPD-stimulated short-term cultures. Lo/PHA cells were found to be less viable than Hi/PHA cells in unstimulated control cultures. PHA improved the viability of Lo/PHA cells while inducing proliferation of Hi/PHA cells with the appearance of more and larger lymphoblasts in the latter. PPD only improved the viability of spleen cell cultures, more so for the Hi/PHA line. The interline difference in thymidine uptake was smaller after PPD than after PHA stimulation. Modifications of culture conditions designed to decrease the interline difference in cell viability lessened but did not abolish the separation between the two lines for the PHA response as measured by thymidine uptake.

T-dependent B-cell activation is signalled by an early increase in potassium influx

When splenic lymphocytes from RNC nu/+ mice were enriched for T cells by lectin purification, mixed to constant cell density with splenocytes from syngeneic nude mice, and cultured with ConA, a proliferative response ensued which was greater than that expected from the T cells alone. This was shown both by incorporation of 3H-thymidine after 48 h of culture and by uptake of potassium (measured as 86Rb) after 15 h. Analysis of metaphase chromosomes stained with Hoechst dye 33258 from co-cultured T-enriched and nude lymphocytes (from female and male donors, respectively) mixed in the proportion 1:4 showed that 40% of the mitotic cells came from nude spleen. About half of the blast cells in such mixtures stained strongly with fluorescein-coupled goat anti-mouse immunoglobulin; T-cell blasts did not stain under these conditions. Treatment of the nu/nu cells with anti-Thy 1.2 and complement had no effect on their subsequent proliferation in coculture. B lymphocytes from nude mouse spleen were therefore activated to proliferate in this system. This B-cell activation can be detected by increased potassium uptake 15 h after the initiation of co-culture. Thus the increased monovalent cation flux (previously demonstrated when B and T lymphocytes were separately stimulated) also occurs when B cells are stimulated through cooperation with mitogen-activated T cells, and is also detectable early in culture. T-dependent activation of B cells is therefore detectable considerably earlier than by conventional assays (such as plaque formation).

Evaluation of murine thymocyte stimulation using a defined culture medium

The ability of RPMI 1640 enriched with FCS or AATSZ (L-alanine, BSA, human transferrin, zinc chloride, and sodium selenite) to support mitogen-induced activation (G0-G1 shift) and proliferation (G1-S shift) of thymocytes has been investigated. The two culture media were found to be equally supportive. In terms of viability, differences were detected in the number of recovered viable cells, but this could be related to alterations in adherent properties, rather than viability of the cells. For the examination of a PHA-induced proliferation, IL-1-containing suppernatants, deriving from normal or induced peritoneal macrophages, were prepared. The supportive capacity of these preparations showed no significant difference between AATSZ and FCS. Despite the excellent supportive capacity for the mitogen-stimulated thymocyte cultures, the AATSZ medium was not able to support all established cell lines tested. A T cell (MOLT 4F) and a macrophage cell line (SK 1) grew equally well in AATSZ- and FCS-enriched medium, but a B cell (U 266) and a null-cell line (Reh) did not proliferate at all. When cells from the latter two lines were cultured in AATSZ medium, they did not complete the RNA-synthesis required for DNA-synthesis, as judged by cytofluorography. From the experiments presented it is concluded that the AATSZ medium offers several advantages, such as easy standardization of culture conditions, and no essential disadvantages for studying mitogen-stimulated thymocytes in vitro. On the other hand, some lymphoid cell lines do require culture conditions that the AATSZ medium cannot provide.

The influence of serum on lymphocyte cultures. II. Cell cycle specificity of serum action in spleen cells

Serum exerts several effects in lymphocyte cultures, one of them being manifested very early. The presence of fetal calf serum (FCS) results in a markedly higher thymidine uptake within a few minutes, as compared with serum-free cultures. On the other hand, the uptake of uridine and other purine bases seem to be little influences by serum. Experiments comparing the uptake of thymidine into the cytoplasm or into trichloroacetic acid-precipitable material suggested that the intracellular thymidine pool increases in size when FCS is added. Using a Lineweaver--Burk plot for thymidine and uridine uptake over a 4-h period, no changes in uridine uptake were observed in the presence of FCS; on the contrary, serum induced an increased Vmax for thymidine, whereas Km remained constant. Cytofluorographic quantitation of G0 and G1 cells indicated that cells disappear more rapidly from the G1 phase in the presence of FCS. The addition of hydroxyurea to the cultures prevented this disappearance. The results taken together strongly suggest that serum contains a factor promoting the shift of G1 cells into the S phase. When a 4-h culture period was used, all sera from different species tested at low concentrations appeared to contain this activity.

Separation of AKR mouse thymus lymphoma from normal thymic cells by centrifugal elutriation

The rapid separation of large numbers of viable thymus cells from AKR mice bearing transplanted or spontaneous thymic lymphomas was achieved by centrifugal elutriation. Separation of more than 3 x 10(8) cells from either a transplanted lymphoma, designated 720, or from a spontaneous thymic lymphoma, required only 15 min. Unfractionated thymus cells obtained from mice bearing the transplanted lymphoma consisted of 80% lymphoma cells (by immunofluorescence for the viral protein, gp70) and 20% normal cells. Fractions of slowly sedimenting cells consisted almost exclusively of normal cells (95%) with modal volumes of 95 micrometers cubed. Fractions of rapidly sedimenting cells consisted of 95% tumor cells with volumes of 150-400 micrometers cubed. The slowly sedimenting cells were almost exclusively (98%) in the GO- or G1-phase. Fractions of rapidly sedimenting cells contained up to 55% S-phase and up to 30% G2-phase cells. Intermediate fractions contained mixtures of normal cells and small GO- or G1-phase tumor cells. Thymidine uptake by the separated cells was determined. The fractions containing normal cells showed little thymidine uptake after 4 and 48 h in culture, while the fractions of tumor cells showed high levels of incorporation. In contrast to the high levels of thymidine uptake by the tumor cell fractions after 48 h in culture, there was little uptake by the unseparated cell suspension, suggesting a possible interaction between normal and tumor cells during the culture period.

Characterization of mouse thoracic duct B lymphocytes. I. Evidence of functional heterogeneity

Thoracic duct lymphocytes (TDL) from C3H/Tif and BALB/c mice were studied for their in vitro reactivity to the B cell mitogens lipopolysaccharide (LPS) and lipoprotein (LP). Roughly 4% and 10% of the surface immunoglobulin (Ig)-positive cells in these populations could be stimulated by LPS and LP, respectively, to generate clones of IgM-secreting cells. Among LPS-reactive B cells, roughly 30% developed into clones which also produced IgG3 or IgG2, while only a very small fraction (1-2%) of all precursors could give rise to clones secreting IgG1 and IgA. Freshly collected TDL from some batches of C3H/HeJ mice displayed a high proportion of Ig-containing B cell blasts (5-10%), which did not secrete enough Ig to be detected as plaque-forming cells (PFC). These cells, however, under appropriate culture conditions and stimulated by LP (but not by Nocardia mitogen), differentiated to PFC of the various Ig classes without dividing.

The induction of suppressor T cells by concanavalin A is independent of cellular proliferation and protein synthesis

Factors that govern the induction of suppressor T cells after stimulation with concanavalin A (Con A) were investigated in a two-stage culture system. Normal mouse spleen cells were incubated with Con A in the presence of a variety of drugs and then assayed for suppressive activity by means of a secondary anti-sheep erythrocyte response in vitro. The inclusion of inhibitors of mitosis (vinblastine sulphate or mytomycin C) or protein synthesis (cycloheximide or pactamycin) into normal spleen cell cultures containing Con A failed to inhibit the subsequent development of suppressor cells. Furthermore, spleen cells from mice previously irradiated with 900 rad or injected with cyclophosphamide expressed a level of suppressor activity after Con A stimulation which was equivalent to that of normal spleen cells. However, the inclusion of drugs that inhibit microtubule or microfilament function (colchicine or cytocholasin B) did prevent suppressor cell induction. Kinetic studies also revealed that significant suppressor activity was detectable in normal spleen cells after only 3 h exposure to Con A. These results indicate that the induction of suppressor T cells in this system is a maturation event involving changes in the cell membrane and is entirely independent of protein synthesis and cellular proliferation.

Effect of indomethacin on in vitro T- and B-cell activation and cell-mediated lysis

The effect of indomethacin, an inhibitor of prostaglandin synthetase, on lymphocyte blast transformation induced by T- or B-cell activators has been studied. Simultaneously adding indomethacin (0.03-0.3 x 10(-6) M final concentration) and concanavalin A to mouse spleen cell cultures, led to an enhancement of 3H-thymidine uptake, whereas 30 x 10(-6) M indomethacin inhibited this uptake. The stimulation induced by indomethacin was higher when this drug was present in the cultures before the addition of the mitogen. Neither the optimal concanavalin A concentration nor the day on which the maximum of 3H-thymidine uptake occurred were altered by indomethacin. Activation of B lymphocytes induced by bacterial lipopolysaccharide was inhibited by indomethacin at all concentrations tested. However, indomethacin similarly blocked the prostaglandin synthesis as well in lipopolysaccharide- or concanavalin A-stimulated lymphocyte cultures. Indomethacin enhanced the one-way mixed lymphocyte reaction. No significant effect of indomethacin was found on cell-mediated cytotoxicity of 51Cr labeled targets. The results are discussed in terms of differential sensitivity of B and T lymphocytes to this anti-inflammatory drug.

Con-A-activated T cells secrete factors with polyclonal B-cell-activating properties

Concanavalin A induced polyclonal antibody synthesis in normal spleen cells in vitro. Optimal responses were obtained by Con A concentrations lower than those optimal for induction of DNA synthesis. T cells, but not macrophages, were necessary for the effect. Spleen cells from nude mice were not activated, whereas cells from the LPS non-responder stain C3H/HeJ were activated to polyclonal antibody synthesis by Con A. Supernatants from Con A activated spleen cells could by themselves induce polyclonal antibody synthesis in untreated spleen cell cultures, even when Con A had been removed by absorption with Sephadex G-50 and when alpha-methyl-mannoside was present in the secondary cultures. T cells produced the active supernatants, which were competent to induce polyclonal antibody synthesis, but not DNA synthesis, in both H-2-incompatible and compatible strains. When the supernants were absorbed with erythrocyte antigens, they specifically induced an enhanced response, in secondary cultures, to the antigen used for absorption. Possible mechanisms of this specific effect are discussed.

Glycoproteins released by Leishmania donovani: immunologic relationships with host and bacterial antigens and preliminary biochemical analysis

The antigenically active glycoproteins (AAGP) released by Leishmania donovani strain 3S promatigotes into growth media and by amastigotes of this strain into the tissue, e.g. blood, of infected hamsters was found to consist of 6 to 7 antigenically distinct components. The antigenic activity of these glycoproteins was resistant to freeze-thawing, protease treatment, and purification by column chromatography using Sephadex G-100. This activity, however, was destroyed by Na periodate and altered by boiling; AAGP adhered firmly to Amicon filter (UM2). The antigenically active substances absorbed UV at 230, 260, 280 nm and gave positive Folin phenol, phenol sulfuric acid, and orcinol reactions. By gel diffusion, the component glycoproteins were found to form lines with concanavalin A and to give reactions to identity and partial identity with human red cells and Mycobacterium butyricum. The possible involvement of the antigenically active glycoproteins in pathogenesis of kala azar is discussed.

A chemical approach to the mechanism of B-lymphocyte activation. I. The pure presentation of haptens does not activate B lymphocytes

In an attempt to definitively determine whether the pure presentation of haptens (on repetitive, non-metabolizable carriers) to B lymphocytes triggers differentiation to antibody-producing cells, dinitrophenyl and trinitrophenyl groups have been covalently coupled to potentially inert carriers (polymethylmethacrylate, chlorinated polyethylene and cellulose). The resulting conjugates (with three different degrees of hapten substitution) are not immunogenic. It is therefore concluded that the pure presentation of haptens to B lymphocytes does not trigger antibody formation.

Different requirements for T cells responding to various doses of concanavalin A

Con A is known to activate T cells to proliferation and the development of effector cells. Conflicting reports have been published as to the need for accessory cells in the T-cell response induced by Con A. We have found that the proliferative response in purified mouse spleen T cells induced by various doses of Con A requires different culture conditions and helper cells. The Con-A-induced response induced by optimal and high concentrations of the ligand requires the presence of either serum or adherent cells obtained from the peritoneal cavity or the spleen. For induction of a proliferative response by low doses of Con A both serum and helper cells must be present. The T-cell response to suboptimal concentrations of Con A is further characterized by the fact that the presence of an Ia-positive cell is required. Removal of Ia-positive cells from purified T cells results in a loss of the response of remaining cells to low doses of Con A but has less effect on the response induced by higher concentrations of the activating ligand. The possibility that distinct subsets of T cells are responding to low and high concentrations of Con A will be discussed.

The polyclonal B cell activator dextran-sulphate induces formation of colony stimulating activity

The effect of dextran-sulphate (DS), a polyclonal activator known to stimulate immature murine B-cells, was assayed in a culture system allowing the growth of myeloid cells. It was known that DS induced the production of a myeloid colony stimulating factor (CSF) by cells from both spleen and bone marrow. Nylonwool purified mouse spleen cells, enriched for T cells, showed a dimished CSF production in response to DS, while CSF production in response to Con A was increased. Furthermore, DS induced CSF in both spleen and bone marrow cells from nude mice. Removal of macrophages did not affect CSF production. The CSF induced was non-dialysable and no small molecular weight or lipoprotein inhibitors could be demonstrated. The results suggest that DS activates cells other than T cells or macrophages (possibly B cells or null cells) to produce a myeloid stem cell stimulating substance. These results indicate that interactions between lymphoid and myeloid cells can take place during differentiation.

Direct activation of guinea pig macrophages by a B-cell mitogen

Since polyclonal B-cell activators (PBA) require macrophages to induce modifications in the lymphocyte in vitro primary response to thymus-dependent antigens, we have investigated whether PBA act directly on macrophages. [14C]glucosamine uptake by guinea pig peritoneal adherent cells after stimulation with purified protein derivative (PPD), lipopolysaccharide (LPS), and dextran sulfate (DxS) was tested. PPD produced an increased [14C]glucosamine uptake, whereas LPS and DxS did not. According to our experiments, (a) PPD does not require the presence of lymphocytes to stimulate macrophages; furthermore, when lymphocytes were present in a concentration higher than 5%, a suppressor effect in the glucosamine uptake was found, and (b) there was no significant difference between the findings when peritoneal adherent cells were cultured in normal medium and in supernatant of lymphocyte cultures stimulated with PPD.