Immunoglobulin synthesis after HLA-identical marrow grafting. V. The role of peripheral blood monocytes in the regulation of in vitro immunoglobulin secretion stimulated by pokeweed mitogen

The ability of purified monocytes to regulate in vitro immunoglobulin (Ig) production was examined in 12 patients after HLA-identical marrow grafting. Five patients were studied less than 3 mo after grafting and seven more than 1 yr after grafting. One of the former had acute graft-vs-host disease and five of the latter had chronic graft-vs-host disease. Ficoll-Hypaque-separated peripheral blood mononuclear cells from patients, normal marrow donors, or healthy unrelated individuals were separated into T and non-T cells by sheep erythrocyte rosetting. Highly enriched monocyte and B cell subpopulations were obtained by placing the non-T cells over discontinuous Percoll gradients. Co-cultures of patient or normal monocyte populations with either normal or patient T and B cells with pokeweed mitogen were performed. A hemolytic plaque assay was used to assess Ig secretion after 6 days of culture. Co-culture of T and non-T cells from 10 of 12 patients failed to produce Ig. Monocyte-enriched fractions from all patients provided normal accessory cell functions when co-cultured with normal T and B cells. Two of five patients with chronic graft-vs-host disease had monocytes that suppressed Ig synthesis at high ratios of monocytes to normal T and B cells. Normal monocyte-enriched fractions did not restore Ig production to T and B cells of patients whose T and non-T cells failed to produce Ig. These data indicate that the observed defects in pokeweed mitogen-driven Ig secretion after marrow grafting are due primarily to defective T and B cell functions and that the monocyte accessory function is intact in most patients studied.     

Evaluation of IgM,IgG, IgA,IgD, and IgE secretion by human peripheral blood lymphocytes in cultures stimulated with pokeweed mitogen and Staphylococcus aureus Cowan I

Sheep erythrocytes coated with staphylococcal protein A were used as target cells in a reverse hemolytic plaque assay. Monospecific antisera to human immunoglobulins G, M, A, D, and E were used to detect each of these classes in cultures of human peripheral blood mononuclear cells stimulated with the polyclonal B-cell activators pokeweed mitogen and Staphylococcus aureus (Cowan I). Both mitogens induced substantial increases in the numbers of cells actively secreting immunoglobulins; in time-course experiments, the peak response was seen on Day 5. The numbers of cell secreting IgM, IgE, and IgD were usually higher in cultures stimulated with S. aureus than with pokeweed mitogen.     

X-irradiation of equine peripheral blood lymphocytes stimulated with phytohaemagglutinin in vitro.

Small lymphocytes were isolated from the peripheral blood of horses and incubated at 37 degrees C in Eagle's medium supplemented with 20 per cent foetal calf serum. The addition of phytohaemagglutinin (PHA) to the cultures resulted in: increased RNA and protein synthesis; the enlargement of the small lymphocyte into a lymphoblast-like cell; the initiation of DNA synthesis, and cell division. When survival was measured 24 hours after X-irradiation by means of phase-contrast microscopy, the lymphoblast-like cell was much more radio-resistant (D0 = 250 rad) than the small lymphocyte (D0 = 20 rad). This increase in radioresistance, however, was not observed until 12-24 hours after PHA treatment. To investigate which of the changes occurring during the transformation of the small lymphocyte was responsible for the increased resistance to irradiation, the percentage of cells surviving irradiation was compared with the percentage of cells incorporating significant amounts of 3HTdR, 3H-UR, or 3H-leucine at the time of irradiation. For this comparison, a dose of 100 rad was used because 100 rad killed essentially all of the small lymphocytes, but less than 35 percent of the cells which had become radioresistant from the PHA treatment. The results indicated that the increase in radioresistance was not associated with DNA synthesis, but instead correlated with the increase in RNA and protein synthesis which the cells had attained at the time of irradiation.     

Control of proliferation in mitogen responsive human peripheral blood lymphocytes: restimulation of cells stimulated by sodium periodate.

Human peripheral blood lymphocytes are stimulated to a greater extent by sodium periodate when cells are incubated in medium containing human serum than when incubated in medium with fetal calf serum. NaIO4 STIMULATION CAN BE REVERSED BY TREATMENT WITH SODIUM BOROHYDRIDE BUT CELLS ALREADY COMMITTED TO DIVISION ARE NOT AFFECTED BY BOROHYDRATE TREATMENT. Maximal commitment to DNA synthesis of a NaIO4 oxidized cell suspens-on occurs after about 28 hr of incubation in medium. The committal time after periodate stimulation is identical to that after stimulation with concanavalin A. Cells treated with periodate and then reduced with borohydride immediately after oxidation are refractory to further per-odate stimulation. Cells stimulated with periodate and then incubated for 6 hr before treatment with borohydride can be restimulated with periodate, indicating a turnover of membrane sites in the 6 hr period. Periodate-stimulated cells divide only once in response to the stimulation. The progeny of cells which were stimulated with periodate can be restimulated by treatment with either periodate or concanavalin A.     

Sequential proliferation induced in human peripheral blood lymphocytes by mitogen. I. Growth of 1000 lymphocytes in feeder layer cultures.

A culture system is described in which 1000 human peripheral blood lymphocytes diluted in 2.5 x 10(5) mitomycin-treated autologous cells respond to phytohemagglutinin (PHA). Proliferation data, including 3HTdR uptake, cell survival counts, and mitotic indices, indicate that this inoculum expands from 1000 to 40,000 cells by day 7, suggesting five or six sequential cell divisions. Chromosome markers in allogeneic cultures demonstrate that the dividing cells are derived from the original 1000 cells and not from the "feeder layer" of mitomycin-treated lymphocytes. The time course of proliferation in this system is similar to that in other human lymphocyte culture systems with a low percentage of responding cells, as in the response to PHA of cells from patients with chronic lymphocytic leukemia or the response of normal lymphocytes to antigens. The conditions provided by the feeder layer which permit proliferation of this small number of lymphocytes are not precisely known, but erythrocytes, heat-killed lymphocytes, or inert particles do not provide a satisfactory substitute.     

Influence of human T lymphocytes identified by antibodies to dipeptidyl peptidase IV on differentiation of human B lymphocytes stimulated with Staphylococcus aureus Cowan I and pokeweed mitogen

The influence of human T lymphocytes expressing the enzyme dipeptidyl peptidase IV (DPP IV) was investigated with respect to human peripheral B-lymphocyte differentiation. B cells stimulated with pokeweed mitogen in the presence of DPP IV-positive T cells produced high amounts of immunoglobulin. Moderate amounts of immunoglobulin could be measured when B cells were cultured in the presence of DPP IV-negative T cells. DPP IV defines a T-cell subset partially overlapping the subsets characterized by the differentiation antigens Leu 3a (helper/inducer) and Leu 2a (suppressor/cytotoxic). DPP IV-positive T cells exert, in contrast to DPP IV-negative T cells, high interleukin-2 activity after stimulation with phytohemagglutinin and pokeweed mitogen. To further functionally characterize DPP IV-positive and DPP IV-negative T cells, the helper effects of Leu 3a-positive T-cell subsets, differing in DPP IV expression, were investigated in pokeweed mitogen- and Staphylococcus aureus-driven B-cell differentiation systems. After pokeweed mitogen stimulation, immunoglobulin production was markedly reduced when B cells were cultured in the presence of Leu 3a-positive T cells expressing DPP IV (DPP IV+/Leu 3a+). In contrast, high amounts of immunoglobulin were produced in cultures with Leu 3a-positive but DPP IV-negative T cells (DPP IV-/Leu 3a+). This difference in immunoglobulin production of B cells cultured with DPP IV+/Leu 3a+ and DPP IV-/Leu 3a+ T cells could not be observed in Staphylococcus aureus-stimulated cultures. Here, both T-cell subsets supported terminal differentiation of B cells. We conclude that in the pokeweed mitogen-driven culture systems, DPP IV+/Leu 3a+ and DPP IV-/Leu 3a+ T cells may differ in the production of growth and/or differentiation factors distinct from interleukin-2.     

Maintenance of lymphocyte surface Ig by mitogen stimulation in vitro.

In 4 to 24 hr cultures of rabbit lymphoid cells in medium supplemented with autologous serum, most B cells lost their surface Ig as assayed by rosette formation with anti-Ig antibody-coated erythrocytes. This loss was prevented by adding selected mitogens such as streptococcal mitogen (SM), lipopolysaccharide, and concanavalin A or by supplementing the medium with fetal calf serum. When SM was added at various times to the cultures (1, 2, 3, and 4 hr), it was effective in maintaining the approximate level of Ig-bearing cells present at the time of its addition but was ineffective in restoring the level of Ig-bearing cells present at the time the cultures were intiated. Very small, submitogenic doses of SM were sufficient to maintain the level of Ig-bearing cells. The data suggest that lymphocytes require continuous stimulation to maintain their surface receptors.     

Infection of peripheral blood lymphocytes in sheep with bovine leukemia virus in vitro

Continuous cultivation of peripheral blood lymphocytes from healthy sheep was carried out in vitro with the help of human recombinant interleukin-2. Lymphocytes were concurrently cultivated with the lethally X-rayed BLV-producing FLK culture cells. Electron microscopy and dot-blot hybridization established that sheep peripheral blood lymphocytes were infected with BLV and a full cycle of replication takes place in them. Infection of sheep leukocytes in vitro can be used to study the mechanisms of leukogenesis in vitro.     

Polyamines in lymphocytes from patients infected by human immunodeficiency virus

Lymphocytes from patients with antibodies against the AIDS associated human immuno-deficiency virus (HIV-1) have elevated concentrations of polyamines. Spermidine and spermine are similar in amount in patients with Persistent Generalized Lymphadenopathy (PGL) and overt AIDS, while putrescine is much higher in the latter. Spermidine-acetyltransferase activity is also increased in lymphocytes from patients with PGL. Diamine-oxidase activity is decreased in serum of patients with PGL, but not in those with AIDS.     

Induction and suppression of immunoglobulin synthesis in cultures of human lymphocytes: effects of pokeweed mitogen and Staphylococcus aureus Cowan I

The synthesis and secretion of immunoglobulins by human peripheral blood mononuclear cells in cultures stimulated with pokeweed mitogen or Staphylococcus aureus Cowan I were evaluated by enumeration of cells containing cytoplasmic immunoglobulins and cells actively secreting immunoglobulins, and by quantitation of immunoglobulins released into culture supernatants. The two mitogens caused comparable stimulation of immunoglobulin production; however, in contrast to pokeweed mitogen, S. aureus was active in cultures depleted of T lymphocytes, and its stimulatory effects were resistant to the influence of suppressor T cells generated by co-stimulation with concanavalin A or by preincubation without mitogenic stimulus. These results indicate distinct pathways of induction and suppression of immunoglobulin synthesis for these two polyclonal B cell activators, and suggest that stimulation by S. aureus is less thymus dependent than that induced by pokeweed mitogen.     

Primary in vitro antibody response from human peripheral blood lymphocytes.

A method for the induction of a primary in vitro antibody response from human peripheral blood lymphocytes is presented. Upon cultivation with trinitrophenyl conjugated polyacrylamide beads (TNP-PAA), an anti-TNP response can be obtained as indicated by the appearance of direct plaque-forming cells from day 5 of culture, with a reproducible peak on day 8. These plaques correspond to cells actively producing antibody of the IgM type, as shown by their inhibition by cycloheximide and by anti-human IgM serum, but not by anti-human Fc gamma serum. Their specificity for the TNP hapten can be demonstrated by the effector cell blockade phenomenon, with highly substituted TNP-human IgG. Although the anti-TNP response induced by TNP-PAA in mouse spleen cell cultures appears T independent the same response in human PBL may involve in addition the participation of T cells, since E-RFC depletion before culture led to a markedly decreased number of plaque-forming cells. A significant response could be obtained from the PBL of all of the 30 normal individuals tested. Importantly, the response was reproducible in its magnitude in the six individuals tested in at least three different experiments. Thus, the in vitro stimulation of human PBL by TNP-PAA can be proposed as a reliable test for the study of human B cell function in a specific primary antibody response.     

Phenotypic changes in CD8+ peripheral blood lymphocytes in cats infected with feline immunodeficiency virus

It is well documented that several cell surface molecules of T lymphocytes are altered by immune activation. We previously reported that feline immunodeficiency virus (FIV) infection induces a reduction in CD8beta chain expression of peripheral blood lymphocytes (PBLs) in cats. In this study, we performed three-color flow-cytometric analysis for activation-associated cell surface molecules (CD2, CD11a, CD45RA-like and major histocompatibility complex antigen class II (MHC II)) and light scatters (cellular size and complexity) to examine whether phenotypic changes also occurred in CD4(+) PBLs in addition to CD8(+) PBLs, of five FIV-infected cats and one uninfected cat. It was shown that (i) CD8alpha(+) PBLs, but not CD4(+) PBLs, had a distinct subpopulation with increased CD11a expression accompanying a reduced CD8beta chain and increased intracellular granules (ii) CD8alpha(+) PBLs, but not CD4(+) PBLs, expressed CD45RA-like antigen with diverse expression levels and (iii) MHC II expression was greater in CD8alpha(+) PBLs than CD4(+) PBLs, and the CD8beta chain reduction was correlated with the MHC II decrease within CD8alpha(+) PBLs. These results suggest that FIV infection induces phenotypically heterogeneous subpopulations in CD8(+) PBLs, including activated phenotypes, rather than in CD4(+) PBLs.     

The effects of four mycotoxins on the mitogen stimulated proliferation of bovine peripheral blood mononuclear cells in vitro

The effects of four mycotoxins, T-2 toxin, deoxynivalenol (DON), ochratoxin A (OTA) and fumonisin B1 (FB1) on the response of bovine peripheral blood mononuclear cells (PBM) in vitro to the mitogens concanavalin A (Con A), phytohaemagglutinin A (PHA) and pokeweed mitogen (PWM) were assayed after 4 days' incubation using 3H-thymidine uptake and the MTT bioassay. The concentrations of mycotoxin required to reduce the proliferative response of PBM by 50% for Con A, PHA and PWM as measured by 3H-thymidine incorporation was for T-2 toxin 0.30, 0.40 and 0.18 ng ml-1; for DON 0.07, 0.09 and 0.04 μg ml-1; for OTA 0.10, 0.20 and 0.15 μg ml- 1, and for FB1 35, 18 and 11 μg ml-1M by 50% for Con A, PHA and PWM as measured by the MTT bioassay were for T-2 toxin 2.0, 2.0 and 1.0 mg ml-1; for DON 0.70, 0.50 and 0.50 μg ml-1; OTA 1.5, 1,5 and 1.5 μg ml- 1; and FB1 >50, >50 and 20 μg ml-1 respectively. Further cytotoxicity assays including the LDH bioassay and Trypan blue exclusion were performed only on Con A-stimulated PBM cells after 72 h incubation. With the LDH-bioassay the 50% inhibition levels were T-2 toxin 0.3 ng ml-1, DON 0.4 μg ml- 1, OTA 1.4 μg ml-1 and FB1 3.5 μg ml-1; for Trypan blue uptake the 50% inhibition levels were T-2 toxin 5 ng ml-1, DON 2.3 μg ml-1 and OTA 4 μg ml-1 respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

Human B-cell activation in vitro. T cell-dependent pokeweed mitogen-induced differentiation of blood B lymphocytes.

Human blood lymphocytes were separated into T and non-T cells and cultured with pokeweed mitogen (PWM). It was found that in the absence of T cells no differentiation of B cells into immunoglobulin-containing blasts and plasma cells took place. Moreover, the cell yields and the rate of DNA synthesis and blast transformation were very low. The influence of T cells on PWM-induced B-lymphocyte differentiation was studied in mixtures of T/non-T cells at various ratios. Addition of even a few T lymphocytes caused a considerable stimulation of B cells by all parameters used. The responses of T/non-T mixtures of the original cellular composition were of the same order as those of cultures of unseparated cells. It is concluded that the differentiation of human blood B lymphocytes into cells actively synthesizing immunoglobulins, as induced by PWM, is strongly dependent upon the presence of T cells.