Induction of antibody synthesis in human B lymphocytes by different polyclonal B cell activators: evaluation by direct and indirect PFC assays

Spontaneous plaque-forming human lymphocytes detected with the protein-A plaque assay

A sizable proportion of fresh human blood and adenoid lymphocytes were found to produce antibodies when tested in the protein-A plaque assay of Gronowicz et al. Plaque formation was not caused by release of passively adsorbed immunoglobulin but depended on active immunoglobulin secretion. We have investigated optimal conditions for plaque formation in this test system. Good reproducibility is obtained only if cells to be tested are kept in the cold before assay, since the antibody-forming capacity of these cells is rapidly exhausted at temperatures above 2 degrees C. In blood lymphocytes the number of IgA-producing cells exceeds those of IgG and IgM, whereas in the adenoid IgG plaque-forming cells dominate. Studies on the use of this method for the monitoring of immune responses are in progress.

Monoclonal autoantibodies derived from multiple sclerosis patients and control persons and their reactivities with antigens of the central nervous system

Peripheral blood B lymphocytes of multiple sclerosis (MS) patients and control persons were transformed with Epstein-Barr virus. Antibody production of transformed cells against isolated human myelin was investigated by enzyme-linked immunosorbent assay (ELISA). Cells producing reactive antibodies were cloned and propagated to produce monoclonal antibodies (mAbs). These mAbs did also react with acetone fixed frozen sections of normal human white matter, as determined by indirect immunofluorescence staining. Some of the mAbs derived from MS patients and a control person with a central nervous system cyst agglutinated liposomes made from lipids of a chloroform/methanol extract of human myelin, whereas mAbs derived from four glioma patients were negative in these tests. The reactive antibodies were investigated further using agglutination tests with liposomes made from pure auxiliary lipids (cholesterol and lecithin) or containing in addition either galactocerebroside, sulfatide or a mixture of bovine brain gangliosides. The great majority of myelin liposome agglutinating antibodies reacted with all types of liposomes, including those made from pure auxiliary lipids. Investigations by ELISA suggest that phospholipids are the reactive components, at least for some of these mAbs. Some antibodies reacted with liposomes containing galactocerebroside or sulfatide, others only with sulfatide containing liposomes. Antibodies showing these specificities were only obtained from MS patients.

Cytomegalovirus-infected adherent cells interact synergistically and antagonistically with Staphylococcus aureus protein A in vitro

Cytomegalovirus (CMV) has been shown to exert suppressive effects on the immune response but also to have mitogenic properties. A bacterial product, protein A from Staphylococcus aureus (SpA) was chosen to study possible interactions in vitro between bacterial products and adherent cells incubated with infectious CMV and ultraviolet light (UV)-inactivated CMV. Small amounts of infectious CMV potentiated SpA-induced DNA synthesis and Ig secretion measured by induction of plaque-forming cells (PFC). The reason for this may be that CMV in small amounts may act in synergism with the non-specific mitogen SpA. UV-inactivated CMV did not influence these responses except for a markedly enhanced PFC induction with SpA in lymphocytes from seronegative individuals. This remarkable synergism with SpA was also seen in enriched B cells. No synergism was seen in lymphocytes from seropositive donors. Large amounts of infectious CMV markedly reduced SpA-induced immune responses. Preliminary data suggest that the immunosuppressive effects are mediated by an interleukin 1 inhibitory factor. CMV was not shown to be a polyclonal B-cell activator but may, possibly in small amounts, act as such together with bacterial products, which would explain certain autoimmune phenomena. To conclude, CMV could in interaction with a bacterial product generate both synergistic and suppressive effects on immune response.

Morphological differentiation of human lymphocyte subpopulations following polyclonal stimulation with bacteria and lectin

Mononuclear cells (MNC) were stimulated with different heat-treated gram-positive and -negative bacteria, and the lymphocyte subpopulation interaction, the proliferative response, and the immunoglobulin secretion were analyzed. It can be demonstrated that beta haemolytic streptococci and Staphylococcus aureus have a similar stimulation pattern: early stimulation of helper T cells, cell contacts of helper T cells and B cells, maximum proliferation on day 5 and 7, and Ig secretion peak on day 7. Klebsiella pneumoniae and Yersinia enterocolitica do not cause proliferation, while Ig secretion is seen on day 5. No cell contacts and no T cell stimulation are seen in the Klebsiella culture, whilst Yersinia causes slight helper T cell activation. In contrast, PHA induces strong T cell stimulation, proliferation and expansion of the suppressor T cell subpopulation. Leu 7-positive lymphocytes are not activated by any of these stimulants.

Polyclonal antibody secretion during acute graft-versus-host disease

Spontaneous plaque-forming cells (S-PFC) were followed in 67 bone marrow transplantation (BMT) recipients and 41 controls. Patients with no acute graft-versus-host disease (GVHD) had decreased IgA and IgM S-PFC up to 7 weeks after BMT compared with controls. Patients with acute GVHD had increased IgG, IgA, and IgM PFC compared with controls and patients without GVHD during the first 4 weeks after BMT. The maximum number of S-PFC increased with increasing severity of acute GVHD. However, at diagnosis of GVHD there was no difference in S-PFC in patients who resolved their GVHD or in those who developed more severe GVHD. After 6 weeks, patients with acute GVHD had significantly decreased IgA and IgM S-PFC compared with normal. No major changes in S-PFC were induced during various infections. However, a patient who developed urticaria had a dramatic increase in S-PFC. Patients studied more than a year after BMT had reduced IgM S-PFC compared with controls. It is concluded that S-PFC are reduced after BMT, but markedly enhanced during acute GVHD.

Lipopolysaccharide suppresses immune complex retention by follicular dendritic cells without cytological alterations

Follicular dendritic cells (FDC) are peculiar cells only located inside lymph follicles and which may be characterized by complex dendritic evaginations retaining high quantities of immune complexes by Fc and C3b receptors. After lipopolysaccharide (LPS) injection in mice the retention of gold-labelled immune complexes was abolished in draining lymph nodes. In order to examine the possibility that the transport of immune complexes to lymph follicles was impaired, we isolated FDC from lymph nodes and incubated them in presence of gold-labelled complexes: no or strongly reduced retention was then observed at the ultrastructural level. This LPS-induced impairment of immune complex fixation by FDC is not due to morphological alteration to the cells but to the inhibition of their Fc and C3b receptors. Further, LPS induces changes in the composition of the lymphocyte population in lymph follicles as higher numbers of blast cells and plasmocytes are observed after treatment.

Direct polyclonal activation of human B lymphocytes by the acquired immune deficiency syndrome virus

When B lymphocytes from normal human peripheral blood were incubated for 1 hour with the retrovirus that causes the acquired immune deficiency syndrome (AIDS), the B cells showed marked proliferation and differentiation. Proliferative responses to the virus peaked on day 4 and appeared to be independent of accessory cells. This finding was repeated with three separate viral isolates, one of which was from a patient from Zaire. The magnitude of the observed responses was comparable to that seen with standard polyclonal B-cell activators. This phenomenon may be at least partially responsible for the polyclonal B-cell activation seen in patients with AIDS.

Induction of immunoglobulin secretion and DNA synthesis in human lymphocytes in vitro by cytomegalovirus preparations

Immunoglobulin secretion as evidenced by plaque-forming cells (PFC) in an indirect haemolysis-in-gel assay, and DNA synthesis were induced in human blood lymphocytes by the following preparations of cytomegalovirus (CMV): Nucleocapside Nc-CMV antigen, membrane M-CMV antigen, crude C-CMV preparations and CMV-incubated adherent cells. Peak stimulations occurred around day 6 in culture. Nc-CMV and M-CMV only stimulated PFC and DNA synthesis in lymphocytes from CMV seropositive individuals. C-CMV also stimulated lymphocytes from CMV seronegative individuals but gave better responses in lymphocytes from CMV seropositive individuals. CMV-incubated adherent cells occasionally stimulated lymphocytes from CMV seronegative individuals but always in CMV seropositive blood donors. Nc-, M-, and C-CMV gave high numbers of PFC in B cells enriched by sheep erythrocyte sedimentation and in co-cultures of enriched T and B cells. Almost no PFC were induced in enriched T cells. DNA synthesis induced by all the three antigenic CMV preparations increased after removal of adherent cells. Strong DNA synthesis was induced in enriched T cells compared to almost none in enriched B cells. It is concluded that some pure CMV preparations act as antigens and more crude preparations induce polyclonal activation. Different CMV preparations may be used to diagnose CMV, to study immune reactivity against CMV and as a model for CMV infections in vitro.

Activation of human B cells: involvement of surface immunoglobulin as evidenced by two biochemically distinct types of response to Staphylococcus aureus

If activation of human B cells by Staphylococcus aureus proceeds through interaction of surface immunoglobulin with Staphylococcal protein A, then immunoglobulins should be produced that are capable of binding to protein A as a consequence of such stimulation. In the present report it is shown that two biochemically distinct types of response to S. aureus are demonstrable in human peripheral blood lymphocytes. Two types of IgM are produced: IgM capable of binding to protein A, and IgM that does not bind and can be recovered by immunoprecipitation with anti-Ig antibodies. Cloned cell lines produce one of either type of Ig, but not both. Therefore, interaction of protein A with Ig alone cannot account for the stimulatory properties of S. aureus. When S. aureus is used in conjunction with pokeweek mitogen, a synergistic effect between the two mitogens is seen. Under conditions of optimal synergistic stimulation, the increase in immunoglobulin production is seen virtually exclusively in the category of molecules capable of binding to protein A. These results offer strong support for a model where optimal differentiation of human B cells to plasma cells is contingent upon receiving at least two signals: one signal is delivered to the surface immunoglobulin, and one signal delivered to the B cell in a T cell and/or monocyte dependent fashion (B cell growth and differentiation factors).

Interferon induces proliferation in leukemic and normal B-cell subsets

3H-thymidine incorporation following stimulation with interferon (IFN) in vitro was investigated in cell cultures from peripheral blood of patients with chronic lymphocytic leukemia (CLL), spleens from necro-kidney transplants and healthy blood donors. It was demonstrated, that IFN can induce a proliferative response in some normal as well as leukemic B lymphocyte subsets. The responses were not T-cell dependent. The results indicate, that B-cell subsets that proliferate in the presence of IFN, are present in higher proportions in spleen than in peripheral blood, and that they constitute a portion of the leukemic blood lymphocyte pool in some patients with CLL. We have previously demonstrated, that IFN induces varying degrees of transformation and differentiation in blood lymphocytes from a majority of CLL patients. The functional characteristics of different B-cell subsets, and their heterogeneous distribution in leukemia, may be important for the results of IFN treatment in various malignant B-cell disorders.

Congenital X-linked hypogammaglobulinemia and asymptomatic hepatitis B antigen carrier state

Hepatitis occurring in patients with congenital X-linked or common variable hypogammaglobulinemia has been reported to follow a usual pattern of rapid progression from acute hepatitis to either chronic active hepatitis or death. This article describes a 21-year-old black man with congenital X-linked hypogammaglobulinemia who has been known to be a hepatitis B-associated antigen carrier during a 9-year follow up period. Liver enzyme studies are normal. His immunologic studies demonstrate no impairment of cellular immunity. His brother, who has the same disease and lives in the same household, has remained negative for hepatitis B-associated antigen. This patient demonstrates that not all hypogammaglobulinemia patients invariably have a severe clinical course with hepatitis.

The regulatory effect of macrophages on the in vitro synthesis of IgE

The effects of indomethacin or macrophage-depletion on the in vitro unstimulated and pokeweed mitogen (PWM)-induced synthesis of IgG and IgE were compared. The effect on the unstimulated synthesis of IgG and IgE was similar, namely, no effect due to indomethacin and enhancement due to macrophage depletion. In contrast, the effect on PWM-induced synthesis was dissimilar. Macrophage depletion enhanced IgG but inhibited IgE production. The effect of indomethacin paralleled that of macrophage depletion suggesting the involvement of prostaglandins. It seems that the regulatory effect of macrophages is different in the IgE system compared with the IgG system.

Modulation of human lymphocyte functions by group A streptococci

Intact (heat-inactivated) bacteria and isolated cellular components of pathogenic group A (M type 5 or 12). B. C. and G streptococci were used to evaluate the in vitro reactivity of mononuclear cells (MNC) from peripheral blood of healthy donors and from human tonsils. High doses of A-streptococcal cells, cell walls, and cell membranes stimulated DNA synthesis, production of leukocyte migration inhibitory factor (LIF), and immunoglobulin (Ig) secretion in MNC from all donors. A streptrococci stimulated higher proliferation rates and larger numbers of plaque-forming cells (PFC) in tonsil cell cultures than in blood MNC cultures. Polyclonal activation of both tonsil and blood B lymphocytes by A-streptococcal cell components was T cell and monocyte dependent, thus showing a similarity between these structures and pokeweed mitogen (PWM), which is a polyclonal T-cell activator (PTA). Cocultivation studies demonstrated that, in the presence of A streptococci, precultured MNC and T cells can suppress the blastogenic and PFC responses of autologous fresh MNC stimulated by phytomitogen or antigen, which is very similar to the concanavalin A (Con A)-induced activation of suppressor cells. In contrast, similar group B-, C-, and G-streptococcal cell envelope biostructures failed to activate blood or tonsil lymphocytes to proliferate, differentiate, or produce LIF.

Polyclonal activation of immunoglobulin secretion without prior DNA synthesis in human B lymphocytes induced by Klebsiella pneumoniae

The capacity of various cell preparations of Klebsiella pneumoniae K43 (Klebs) to induce [3H]thymidine uptake and immunoglobulin (Ig) secretion by human mononuclear blood cells (MNC) and their lymphocyte subpopulations was investigated. All Klebs preparations were virtually devoid of mitogenic properties, in contrast to control preparations of pokeweed mitogen (PWM) and group A streptococcal cell membranes (A-ScM). Klebs induced differentiation of B cells into Ig-secreting cells. B-cell populations that were sufficiently depleted of T cells to be unresponsive to A-ScM ("highly purified B cells") showed a marked response to Klebs. Similarly, the number of plaque-forming cells (PFC) in Klebs-driven cultures did not change after restitution of T cells, whereas the presence of restituted T cells augmented the B-cell response to PWM and A-ScM. Radical removal of adherent MNC ("monocytes"), however, completely abrogated the PFC response and [3H]thymidine uptake of both MNC activated by Klebs and MNC activated by PWM or A-ScM.

Are increased IgE-levels a signal of an acute graft-versus-host reaction?

IgE-levels are markedly elevated following bone-marrow transplantation in patients with and without GVHD. In patients with GVHD, there is a significant correlation between the timing of the IgE-increase and the appearance of clinical GVHD (p less than 0.01). The highest IgE-level (8000 kU/l) was noted in a recipient of a syngeneic graft. During the IgE-peak, the serum from this patient contained low concentrations of IgE reacting with several tested allergens as well as for the hapten TNP, which indicated polyclonal activation. In a patient with a known allergy to animal danders, RAST tests were positive against dog and cat both before and six weeks after total body irradiation and transplantation with marrow from a non-allergic donor. A slight increase in the amount of allergen-specific, IgE-antibodies was seen during the increase in total IgE. A non-allergic patient was transplanted with marrow from a donor allergic to timothy. Timothy-specific, IgE-antibodies were detected immediately after transplantation but they disappeared within a few days and could not be detected during the period of increase in total IgE. We believe that the IgE-elevation seen after conditioning with cytotoxic drugs and total body irradiation in BMT-patients is a polyclonal response in host B-cells induced during an acute, GVHR and influenced by disturbed regulatory T-cells. Lymphocytes from patients with acute GVHD had unusually large numbers of IgG/PFC in vitro after stimulation with staph. aureus Cowan 1 (p less than 0.001), which may reflect a clonal expansion of responsive B-cells.

Mitogen-induced switching of immunoglobulin heavy-chain class secretion in chronic B-lymphocytic leukaemia and immunocytoma cell populations

Lymphocytes from peripheral blood, bone marrow, and lymph nodes from six patients with chronic B-lymphoproliferative disease were studied. Two of the patients had a polymorphic immunocytoma with surface membrane immunoglobulin phenotype mu kappa. Four patients had chronic B-lymphocytic leukaemia (CLL) with the phenotypes mu kappa, mu delta kappa, mu lambda, and mu delta lambda, respectively. In no case did the monoclonal cell populations express gamma chains on the surface, and none produced monoclonal immunoglobulin in vivo. The malignant B lymphocytes were cultured in the presence of polyclonal B-cell activators. Immunoglobulin secretion was detected with the protein A plaque assay and with a modification of the reversed haemolysis-in-agar plaque assay. Immunoglobulin secretion was induced in four of the cell populations. In both the immunocytomas and in one of the CLL cell clones the heat-inactivated Staphylococcus aureus strain Cowan I induced secretion of IgG, as well as IgM, associated only with the same light chain as was expressed on the surface of the unstimulated cells. Thus, mitogens can induce immunoglobulin secretion in vitro in malignant B lymphocytes, and Cowan I bacteria also have the ability to induce a switch of immunoglobulin production from IgM to IgG in a fraction of the leukaemic cell populations.

Cytofluorographic analysis of pokeweed mitogen-stimulated human peripheral blood cells in culture: age-related characteristics

By use of monoclonal antibodies and flow cytometry techniques, peripheral blood mononuclear cells from young (20-30 years) and elderly (70+ years) subjects were analyzed before and after culture with pokeweed mitogen to gain insight into the cellular interactions responsible for the decreased B cell response observed in culture samples from the elderly. Data analysis of surface immunoglobulin-positive cells demonstrated no difference in the percentage of B cells in the elderly, while both plaque-forming cell and intracytoplasmic immunoglobulin assays showed significantly reduced B cell maturation (P = less than 0.01) compared with young controls. The B cell defect was shown to be functional and not a result of failure to proliferate and survive during incubation. Surface marker analysis of T cell subpopulations demonstrated a definite shift (P = less than 0.01) in the helper/suppressor T cell ratio in cultured samples from the elderly group (3.9) compared with young subjects (1.2). In addition to the absolute increase in the helper T cell population, forward-angle light scatter analysis demonstrated that, compared with young controls, a greater portion of the helper T cell population in the elderly subjects had characteristics of activated, blast-sized cells. The data reported in this study suggest that in the elderly group there is a functional immunoregulatory imbalance in the helper T cell subset.

Staphylococcal peptidoglycan: T-cell-dependent mitogen and relatively T-cell-independent polyclonal B-cell activator of human lymphocytes

Staphylococcal cell wall products have been widely examined as probes for dissection of in vitro human immune responses. Mitogenic and polyclonal B-cell-activating properties have been attributed to intact cell walls or the protein A constituent thereof. We now report that staphylococcal peptidoglycan (PG), the major cell wall constituent, is not only a potent mitogen but also a polyclonal B-cell activator for human peripheral blood mononuclear cells (PBM). PG-induced proliferative responses of human PBM were comparable to that observed in pokeweed mitogen-stimulated cultures. As was true for pokeweed mitogen, PG-induced proliferation required the presence of T-cell help. Cultures of human PBM with PG also resulted in B-cell differentiation as reflected by an increase in numbers of immunoglobulin-secreting cells in stimulated cultures. In contrast to the proliferative response, PG-induced B-cell differentiation was relatively T-cell independent. This point became apparent when B-cell fractions were partially depleted of excessive numbers of monocytes before culture. Also, B-cell proliferation did not appear to be a major prerequisite for PG-induced B-cell differentiation responses. These data indicate that PG is a potent T-cell-dependent mitogen and relatively T-cell-independent polyclonal B-cell activator of human lymphocytes.

Human peripheral blood lymphocyte activation by protein A from Staphylococcus aureus

Mitogenesis and polyclonal immunoglobulin production in peripheral blood lymphocyte cultures activated with Formalin-fixed or autoclaved protein A-containing Staphylococcus aureus were studied. Direct evidence for a dissociation between cell proliferation and polyclonal immunoglobulin production was found, in that S. aureus was not mitogenic after being autoclaved but retained the ability to stimulate B cells to produce immunoglobulin. Trypsin-treated S. aureus lost its binding site for immunoglobulin G, but its mitogenicity was not altered; thus, the protein A binding site for immunoglobulin G on the bacterial cell wall is not required for the stimulation of lymphocyte proliferation. Our data also show a dissociation between cell proliferation and polyclonal immunoglobulin production induced by protein A coupled to Sepharose CL-4B. These results suggest the presence of three distinct active sites on the protein A molecule: one that binds immunoglobulin G molecules, one that stimulates cell proliferation, and one that stimulates polyclonal immunoglobulin production.

Functional characteristics of synovial fluid and blood mononuclear cells in rheumatoid arthritis and traumatic synovitis

The activity of blood mononuclear cells (BMC) and synovial fluid mononuclear cells (SMC) from patients with rheumatoid arthritis (RA) and traumatic synovitis (TS) was assessed by means of [14C]thymidine incorporation and production of leukocyte migration inhibitory factor (LIF). When compared with normal controls, spontaneous LIF production by BMC was found in 5 of 9 TS patients, whereas spontaneous LIF production by rheumatoid arthritis BMC and by SMC from both patient groups was infrequently seen. ConA-induced LIF production by BMC and SMC from both patient groups did not differ significantly from that of normal controls. Thymidine incorporation by unstimulated SMC and BMC was low in both patient groups. After stimulation with polyclonal activators, SMC showed significantly reduced proliferation in comparison with BMC, but the responses to microbial antigens were equal to or higher than those of BMC. The proliferative responses of stimulated SMC from TS patients were higher than the responses displayed by stimulated SMC from RA patients.

Polyclonal B-cell activation induced by extracts of Gram-negative bacteria isolated from periodontally diseased sites

The objective of this research was to determine whether gram-negative bacteria frequently isolated from periodontally diseased sites contained polyclonal B-cell activators. Polyclonal B-cell activation, which results in nonspecific activation of multiple B-cell clones was analyzed by a hemolysis-in-gel assay designed to detect a broad range of antibody specificities. Extracts from numerous bacterial strains, including Bacteroides gingivalis, Bacteroides melaninogenicus subsp. melaninogenicus, B. melaninogenicus subsp. intermedius, Fusobacterium nucleatum, Selenomonas sputigena, Capnocytophaga ochracea, and Actinobacillus actinomycetemcomitans, were tested. Extracts of the above organisms were found to stimulate polyclonal antibody responses in cultures of normal human peripheral blood lymphocytes, although the magnitude of stimulation varied among the extracts. Optimal antibody-forming cell responses were found at stimulator doses between 5 and 1,000 micrograms/ml. We conclude that the resident gram-negative subgingival flora associated with periodontal lesions possesses potent polyclonal B-cell activators. These activators may contribute to disease pathogenesis by inducing B lymphocytes to produce antibody, osteolytic factors, or both and possibly other mediators of inflammation.

Immunological features of psoriasis. Effects of Ro-109359, concanavalin A, pokeweed mitogen, and methotrexate on cultivated lymphocytes

Isolated peripheral mononuclear cells of psoriasis patients with different disease characteristics, e. g. head-localised, quiescent guttata, confluent active widespread and erythrodermic, were cultured in a modified Mishell-Dutton system. Using the plaque-forming cell (PFC) assay, single cell antibody formation was studied, and class distribution monitored, adding pokeweed mitogen (PWM), concanavalin A (ConA), methotrexate (MTX) or Ro-109359/31, as well as autologous sera to the culture. PFC-estimation vs. sheep red blood cells (SRBC) and burro red blood cells (BRBC) revealed a distinct suppression of primarily IgG-PFC in some of the PWM-treated patients' cultures; ConA maximally reduced PFC by only 50%, compared to 100% for normal immune cells. Ro-109359/31 reduced mainly IgG-PFC in the co-cultures with PWM or autologous sera. MTX resulted in a reduction of IgG-PFC and IgM-PFC equally. The results were compared with cultured immune cells from normal individuals. The two antigenically different indicators, the partial abolition of ConA induced suppression, broad-based immunoglobulin elevation in the sera, and the mainly IgG-formation hint at the role of polyclonal B-cell activation in the perpetuation of psoriasis, which can be specifically reduced by Ro-109359/31. Suppressor cell dysfunctions remain to be discussed.

The use of hemolysis-in-gel assays to study polyclonal antibody secretion in bone marrow transplant recipients

Polyclonal antibody secretion was measured as direct plaque-forming cells (PFC) against fluorescein isothiocyanate coupled sheep red blood cells (FITC-SRBC) or in an indirect assay using protein A coupled SRBC and anti-sera against human IgG, IgA, and IgM. Eighty individuals who were recipients of bone marrow transplants and 66 healthy controls were studied. Lymphocytes from patients studied during the first three months (short-term patients) had deficient B-cell function in both assays compared to normals. In healthy controls the direct assay only detected about 4% of the IgM producing B cells found in the indirect assay. PFC in long-term patients were not different from that of controls except for patients with chronic graft-versus-host disease (GVHD) who had a deficient IgM production. Patients with acute GVHD had unusual high numbers of IgG PFC after Staph. aureus activation (p less than 0.001). Short-term patients with infections had increased (p less than 0.01) IgG and IgA after Staph. aureus activation. PFC assays performed in three patients with grafts from HLA-nonidentical donors showed an increase in the background cultures for IgG PFC (p less than 0.025) and an increased IgG PFC after Staph. aureus stimulation (p less than 0.01) compared to patients with HLA-identical donors.

Polyclonal antibody secretion induced in human mixed lymphocyte cultures

In mixed leucocyte culture (MLC), using human spleen cells or thoracic duct lymphocytes, antibody secretion was induced, measured as plaque-forming cells (PFC) in a haemolysis-in-gel assay with fluorescein isothiocyanate (FITC)-coupled sheep erythrocytes (SRBC) as targets. Peak antibody secretion was seen on day 5. Using protein-A-coupled SRBC as targets and developing antisera, antibody secretion in MLC was found to be of IgM, IgG and IgA type. There was no correlation between the number of PFC against FITC-SRBC in MLC and DNA synthesis. Supernatants from MLC failed to induce antibody secretion.

Covariances of mitogenic responses in leukaemic blood lymphocytes: a functional marker system for the human B lymphocyte differentiation

Various polyclonal activating substances have been shown to stimulate human chronic lymphatic leukaemic (CLL) cells to undergo blast transformation, to divide and to secrete monoclonal immunglobulin. CLL cells from different patients show distinct response patterns to these ligands. We have statistically analysed these response patterns and found that responses to certain ligands demonstrate covariance; that is, a high response to one ligand is statistically associated with a high response to another ligand. A factor analysis of these data on the basis of responses of CLL cells from twenty-one patients and from the use of five different ligands in three different concentrations has shown that as few as two factors can account for as much as 63% of the total variance of these responses. On the assumption that these two factors were T-cell dependency of CLL responses and stage of maturity of the responding CLL cell, we have formulated a theory that explains the basis for this functional marker system for CLL cells. It is possible application to the characterization of individual CLL clones has been discussed.