Polyclonal activation of bone-marrow-derived lymphocytes from human peripheral blood measured by a direct plaque-forming cell assay

Antibody production and DNA synthesis of human lymphocyte subpopulations induced by PPD tuberculin

Purified protein derivative (PPD) of tuberculin was found to induce antibody secretion and DNA synthesis in human lymphocytes from blood, spleen, tonsil and lymph node. Antibody secretion was measured as plaque-forming cells (PFC) against fluorescein isothiocyanate (FITC) coupled sheep red blood cells (SRBC) in a haemolysis-in-gel assay. Peak antibody secretion by 100 micrograms/ml of PPD was usually seen on day 6 for blood lymphocytes, and varied from day 3 to day 6 for spleen cells. Peak DNA synthesis for blood lymphocytes stimulated by various concentrations of PPD ranged from day 4 to day 7. The highest number of PFC in tonsil and spleen cells was induced by PPD compared to Staphylococcus aureus bacteria Cowan 1, lipopolysaccharide (LPS) and pokeweed mitogen (PWM). Antibody secretion by PPD was not affected when phagocytic cells were removed by iron treatment. PPD stimulated a higher DNA synthesis in unseparated lymphocytes or mixtures of T and B cells than in enriched T or B cell suspensions. PPD did not induce PFC in B cells enriched by the removal of sheep erythrocyte rosette-forming cells (E-RFC). However, more PFC were stimulated by PPD in enriched E-RFC compared to unseparated lymphocytes, which may indicate that most of the FITC-SRBC reactive B cells also form rosettes with SRBC.

Human B cell function in a polyclonally induced plaque forming cell system. Cell triggering and immunoregulation

The use of a sensitive PFC assay against a specific antigenic determinant (SRBC) following polyclonal triggering of human lymphocytes has provided a unique insight into the complex mechanisms of triggering of human B cells. The system is under the strict regulation of a delicate balance between helper and suppressor influences reflecting in certain circumstances the activity of distinct subsets of immunoregulatory cells. Lymphoid cells in certain diseases characterized by disordered immunoregulation, when as system, may in effect be manifesting an abnormal expression of immunoregulatory mechanisms operable in normal immune responses. In vivo activation of lymphoid cells by PBAs may have an important role in disease states as well as in the subsequent in vitro expression of B cell function. Furthermore, it is quite possible that under certain circumstances some B cell responses which appear to be purely antigen-specific may be reflections of synergy between PBA substances and specific antigen. The use of PBAs as probes and sensitive PVC systems as assays has already proven fruitful in the dissection of the complex mechanisms of nonspecific B cell triggering in man and may indeed ultimately lead to an understanding of the mechanisms of specificity of immune reactivity.

Use of a human plaque-forming cell assay to study peripheral blood bursa-equivalent cell activation and excessive suppressor cell activity in humoral immunodeficiency

A plaque assay that detects human mononuclear blood cells producing immunoglobulin (Ig)M antibody to sheep erythrocytes was investigated for its usefulness in studying B-cell activation and regulation in 24 patients with humoral immunodeficiency. Cells from 3 of 15 patients with common variable agammaglobulinemia produced some plaques (range 40--160/10(6) cells; normal range 80--1240/10(6)), but those from the other 12, from all 7 with x-linked agammaglobulinemia and from the 2 with x-linked immunodeficiency with hyper-IgM failed to produce any detectable plaques. In co-cultures of patient and normal cells a very good correlation was seen between results of the plaque assay and an IgM biosynthesis assay in detecting excessive suppressor cell activity. Cells from 7 of 15 common variable agammaglobulinemics, from 3 of 7 x-linked agammaglobulinemics, and from both patients with hyper-IgM caused significant suppression of IgM biosynthesis and(or) plaque formation by normal cells. The observations in the last two groups and discordance for excess suppressor activity in identical twins with common variable agammaglobulinemia suggest that the activity develops secondarily to whatever their primary defects may be. Culturing non-T cells from common variable agammaglobulinemics exhibiting excessive suppressor cell activity with normal T cells resulted in plaque formation in four of five patients so studied; in all five the suppressor activity was found in the T-cell population. The availability of a plaque assay for the study of blood cells from immunodeficient patients provides a new probe to examine the cellular nature of such defects.

Endotoxin protein is a mitogen and polyclonal activator of human B lymphocytes

Endotoxin protein (EP) has been shown to be a mitogen and polyclonal activator of human peripheral blood lymphocytes. EP stimulates proliferation of B lymphoyctes in the absence of T cells, and this activation is nonspecific by a number of parameters. Additionally, EP mitogenesis, but not polyclonal activation, is inhibited in the presence of human serum, suggesting that these events are dissociable. In these studies, EP appears to be equivalent to or better than pokeweed mitogen in stimulating nonspecific antibody production in vitro.

Polyclonal activation of human B lymphocytes in vitro by pokeweed mitogen: a simple technique for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production

A simple technique has been worked out for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production from single cultures of 1 X 10(6) human peripheral blood lymphocytes stimulated with pokeweed mitogen (PWM). Kinetic studies showed that number of cells, thymidine incorporation rate, number of plaque-forming cells against fluorescein-isothiocyanate-haptenated sheep erythrocytes and concentration of IgM and IgG in the supernatant peaked on the average between day 5 and 7 of culture. This technique is particularly suitable for the analysis of hypogammaglobulinaemias in infancy.

Activation of human B lymphocytes. VIII. Differential radiosensitivity of subpopulations of lymphoid cells involved in the polyclonally-induced PFC responses of peripheral blood B lymphocytes

The differential effect of various doses of irradiation on subpopulations of human peripheral blood lymphoid cells involved in the pokeweed mitogen (PWM) induced PFC response against sheep red blood cells (SRBC) was studied. The plaque forming B cells were quite sensitive to low doses of irradiation with complete suppression of responses at 300 to 500 rad. On the contrary, helper T-cell function was resistant to 2000 rad. Co-culture of irradiated T cells with autologous or allogeneic B cells resulted in marked enhancement of PFC responses consistent with the suppression of naturally occurring suppressor cells with a resulting pure helper effect. Irradiated T-cell-depleted suspensions failed to produce this effect as did heat killed T cells, whereas mitomycin C treated T cells gave effects similar to irradiated T cells. These findings are consistent with a lack of requirement of cell division for a T-cell helper effect and a requirement of mitosis or another irradiation sensitive, mitomycin C sensitive process for a T-suppressor cell effect. These studies have potential relevance in the evaluation of subpopulations of human lymphoid cells involved in antibody production in normal individuals and in disease states.

Optimal conditions for polyclonal antibody secretion and DNA synthesis in human blood and spleen lymphocytes by lipopolysaccharide

Lipopolysaccharides from E. coli (LPS) stimulated increased DNA synthesis and high-rate antibody secretion in human lymphocytes from blood and spleen. Peak DNA synthesis by 10 or 100 microgram/ml LPS was seen on day 6 for blood lymphocytes. Using 500 microgram/ml of LPS the peak response was reached on day 5 and with 0.1--1 microgram/ml the maximal stimulation was on day 7. For spleen cells LPS 100 microgram/ml gave a peak stimulation on day 4 or 5. Antibody secretion, measured as plaque-forming cells (PFC) against fluorescein isothiocyanate-coupled sheep erythrocytes in a haemolysis-in-gel assay, was maximal on day 5 in blood lymphocytes and on day 3 or 4 in spleen cells. The highest cell viability and antibody secretion after stimulation with LPS was obtained in 16 mm diameter multiwell plates usng 2.5 x 10(6) cells in 1 ml of medium containing 10% AB serum absorbed with SRBC. Feeding of cultures was essential for stimulation of blood lymphocytes but not for spleen cells.

Many bacterial species are mitogenic for human blood B lymphocytes

Thirty bacterial species were tested for their ability to stimulate to increased DNA synthesis in human blood lymphocytes. A definite stimulation was obtained with eighteen bacterial species. For three of these species ten different strains of each were tested, and all increased DNA synthesis. The maximum response was after 3--4 days of culture, suggesting a mitogenic effect. This was confirmed by the induction of polyclonal antibody production shown by a plague assay, which was positive for nine of eleven species tested. Most bacterial species increased the DNA synthesis in B-lymphocyte-enriched and unseparated lymphocytes but had negligible activity on T-lymphocyte-enriched cultures. Among bacteria with a mitogenic effect and ability to induce polyclonal antibody production are Staphylococcus aureus strain Cowan I with a high content of protein A and many common human pathogens such as Haemophilus influenzae, Mycobacterium tuberculosis, Neisseria gonorrhoeae, Streptococcus group A and Streptococcus pneumoniae.

Inhibition of polyclonal B-cell activation by suppressor monocytes in patients with sarcoidosis

The present study employed a direct plaque-forming cell (PGC) assay following pokeweed mitogen (PWM) induced polyclonal activation of B lymphocytes in sarcoidosis to evaluate the in vitro humoral immune response in this disease and to delineate the immunoregulation of this response. Sarcoidosis lymphocytes had a suppressed PFC response to polyclonal activation, but were unable to suppress normal B-cell PFC responses in allogeneic co-cultures. Removal of a cell type, which was corticosteroid-resistant, radio-resistant, adherent and a non-T cell, from sarcoidosis mononuclear cell suspensions reversed the suppressed PFC response, indicating the presence of a suppressor monocyte. Thus in vitro suppressor cell activity has now been demonstrated in this disease, which is characterized by multiple immunological aberrancies.

Activation of human B and T lymphocytes by protein A of Staphylococcus aureus

Protein A from Staphylococcus aureus, in soluble form or coupled to Sepharose beads, acts as a polyclonal B cell activator (PBA) for human lymphocytes in blood and spleen. PBA activity was demonstrated in spleen cells by the ability of protein A to induce the formation of intracellular immunoglobulin synthesis and to activate polyclonal antibody secretion demonstrated against fluorescein isothiocyanate-coupled sheep erythrocytes in a modified hemolysis in gel assay. More plaqueforming cells (PFC) were seen in unseparated cells than in purified B cells. In blood lymphocytes, only few PFC were activated by soluble protein A. Protein A increased DNA synthesis in blood and spleen cells. At a concentration of 100 microgram/ml the peak response was on day 4 or 5, but at 1 microgram/ml the peak response occurred later. On day 4 of culture, high mitogenic activity was seen in unseparated lymphocytes or mixtures of separated B and T cells, whereas in enriched B and T cell suspensions activity was low. On day 7, however, DNA synthesis in both the enriched B and T cells was higher than in mixtures of B and T cells. Protein A stimulated DNA synthesis in thymus cells with a peak response on day 6. It is concluded that protein A alone or as an IgG complex can activate both B and T cells, though the mechanism of activation is not known and may be different for B and T cells.