Induction of an antibody response in cultures of human peripheral blood lymphocytes

A Few Key Historical Events in the Antibody Field: The Alacritous Antibody

We have coined the term "alacrity" to describe the extraordinary diversity of B cell activation potentials, even among cells in a single B cell clone responding to a single antigen. The discovery of methodologies for B cell culture in limiting dilution allowed scientists to identify the source of cellular heterogeneity among cells of the immune system. Analyses of individual B cells set the stage for more detailed descriptions of the factors that diversify B cell functions, some of which will be expanded upon by partner articles in this B cell issue.

Mononuclear phagocytes from patients with active systemic lupus erythematosus down-regulate the specific in vitro reactivity of autologous lymphocytes to double-stranded DNA

Peripheral mononuclear cells (MNC) from patients with systemic lupus erythematosus (SLE) are hyporesponsive in vitro. In order to study the role of mononuclear phagocytes (m phag) in regulating the in vitro responses of autologous lymphocytes, the MNC from 16 SLE patients (eight active, eight inactive) and 14 healthy controls were stimulated in vitro with PHA or dsDNA. The proliferative response to PHA was tested by 3H-thymidine incorporation on day 4 and the response to dsDNA using a specific haemolytic plaque assay. Indomethacin, an inhibitor of prostaglandin (PG) synthesis by m phag, was added into the cultures to test the presence of suppressive m phag acting through a PG-mediated pathway. Indomethacin augmented the proliferative response to PHA in active SLE cultures and not in inactive SLE or controls. In six of 13 SLE cultures, dsDNA totally or partly suppressed anti-dsDNA plaque-forming cell (PFC) generation. Indomethacin restored or enhanced the PFC response to dsDNA in active SLE and not in inactive SLE or controls. M phag depletion by plastic adherence prevented the effects of indomethacin. These results show that m phage exerting a suppressive activity on PHA-induced lymphocyte proliferation and on anti-dsDNA antibody production are found in cultures from active SLE and generally not in inactive SLE or healthy individuals. PHA being primarily a T-cell stimulator, the m phag suppressive activity observed in PHA-stimulated cultures is exerted on T cells. On the other hand, in two active SLE cultures depleted of T cells by OKT3 antibody, indomethacin still could enhance the PFC response to dsDNA, showing that in vitro suppressive m phag can act directly on B cells from patients with active SLE.

Production of human--human hybridomas secreting antibody to sheep erythrocytes after in vitro immunization of peripheral blood lymphocytes

This report describes the formation of human hybridomas after in vitro immunization of peripheral blood lymphocytes (PBL) with an antigen and fusion of the stimulated lymphocytes with a HAT-sensitive human myeloma cell line, RPMI 8226. PBL were stimulated in vitro with sheep erythrocytes (SRBC) plus fresh human serum. PBL of some donors produced anti-SRBC antibody when they were cultured at 2 X 10(6) cells per well in a 24-well plate with the antigen plus fresh human serum for 7 days. Although lymphocytes of some donors were "low-responders" under the above conditions, they responded to SRBC when they were cultured with not only the antigen plus fresh human serum but also with the culture supernatant obtained after phytohemagglutinin (PHA) stimulation of a mixture of PBL from two donors (MLC-PHA sup). The cells sensitized by this procedure were fused with RPMI 8226 cells. Hybrids secreting IgM or IgG anti-SRBC antibodies were obtained. Additionally the ratio of total IgG-producing hybridomas to IgM-producing ones was higher when the MLC-PHA sup was used at the time of the in vitro immunization.

Induction of antibody to foot-and-mouth disease virus in presensitized mouse spleen cell cultures

Cultures of spleen cells from immunized mice were stimulated in vitro by soluble preparations of purified foot-and-mouth disease virus. Virus-specific antibody, as detected by an enzyme-linked immunosorbent assay, was produced by immune spleen cells but not by normal, nonimmune cells. The optimal specific response was obtained with 1 microgram of virus per ml of culture; as the virus concentration was increased, the production of specific antibody was reduced. For very low concentrations of virus (less than 0.01 microgram per culture), there was tentative evidence of suppression of the specific antibody response. The levels of specific antibody induced were dependent on the source and number of plastic-adherent cells present in the cultures. We intend to use this model system to study further the basis of immunity to foot-and-mouth disease virus.

Detection of human in vitro hapten specific antibody responses

A microculture and radioimmunoassay is described which is capable of generating and detecting very small levels of human anti-DNP antibody. The antibody produced is hapten specific and the response is T-cell dependent. The microculture system described avoids the need for high serum supplements, mitogens, in vivo immunisation or large cell numbers. As this system is simple, sensitive and reproducible it has considerable potential in the study of human immune response regulation and especially the role of lymphokines in human antibody responses.

Micro-system for the primary immunization of baboon (Papio cynocephalus) peripheral blood mononuclear cells with sheep erythrocytes in vitro

A micro-culture system for the stimulation of baboon peripheral blood mononuclear cells (PBMC) with sheep erythrocytes (SRBC) in vitro was established. PBMC cultures in 96-well microtiter plates were maintained in 300 microliter of culture medium containing a murine mixed lymphocyte reaction (MLR) supernatant and SRBC. Cultures of 7.5 x 10(5) PBMC and 6 x 10(6) SRBC resulted in the highest anti-SRBC plaque-forming cell (PFC) response. It was also determined that the presence of 50 microliter of murine MLR supernatant was required for optimal PFC generation and that the cultures required supplementation with nutrient cocktail 3 days post-immunization. Although PFC were detectable on days 4-8, the maximum expression of PFC occurred on day 7.

Antigen-specific antibody response induced in cultures of human blood lymphocytes in presence of polyethylene glycol

Human peripheral blood lymphocytes respond in vitro to sheep red blood cells (SRBC) with the appearance of numerous specific plaque-forming cells, if the Epstein-Barr virus (EBV) is added to the cultures together with the antigen. However, it was found that when polyethylene glycol (mol. wt. 6000) is included in the culture medium at a final concentration of 4%, antigen alone is able to induce an anti-SRBC response, with clear hemolytic plaques of regular size. Addition of EBV causes a further increase in the antigen-specific antibody response.

Antibody-forming foci in soft-agar cultures of human peripheral blood cells

Human peripheral blood lymphocytes (PBL) from healthy blood donors were grown in soft-agar gel with sheep red blood cells (SRBC) and autologous plasma as a source of complement. After 4--6 days incubation, foci of proliferating hemolysin-forming cells, surrounded by a lytic area of 0.2--0.5 mm, were detected on the surface of the plates. The response was antigen specific, since new hemolytic areas were observed on pouring a fresh agar-SRBC mixture over the surface of primary cultures, but not on pouring a mixture containing rat or rabbit erythrocytes. The antibody response was significantly increased by addition to the cultures of polyethylene glycol 6000 (PEG), 8% final concentration. The mean number of foci was 8.4 +/- 2.2 in cultures without PEG and 36.2 +/- 2.3 in PEG+ cultures, both containing 9 X 10(6) lymphocytes. This finding is in agreement with observations on the frequency of precursors of antibody-forming cells among lymphoid populations. The explanation of the mechanism by which PEG 6000 modified the immune reactivity of PBL is not clear. However, we think, that this technique provides a reliable methodology for PBL antigenic stimulation in vitro.

Antigen-specific T-cell factors

Antigen-specific T-cell factors are mediator molecules which are produced by helper and suppressor T cells and which can perform the function of those cells in an antigen-specific manner. They probably play an important part in immunoregulation. The major histocompatibility complex has a controlling influence on their structure and activity, while their antigen-recognition properties may be conferred by immunoglobulin V regions. Interest in the factors derives from three related areas of research, namely (i) the problem of T-cell recognition of antigen; (ii) the mechanisms of cellular interactions in antibody production and cell-mediated immunity; and (iii) the genetic control of immune responses. This review discusses the literature up to June 1980 on their production, structure, genetic restriction and mechanism of action.

Suppression of antibody responses in humans infected with Trypanosoma cruzi

Peripheral blood leukocytes from patients serologically positive for Chagas' disease were examined for their ability to respond to heterologous antigens in vitro. It was found that mononuclear cells from chagasic patients had greatly reduced ability to respond to sheep erythrocytes (SRBC) as compared with peripheral blood mononuclear cells (PBMC) from control subjects. The reduction in anti-SRBC antibody activity was independent of antigen dose and was not a result of differences in antibody response kinetics. Depletion of plastic-adherent result of differences in antibody response kinetics. Depletion of plastic-adherent cells from the PBMC of patients did not affect the suppressed state of the nonadherent lymphocytes. No relationship was evident between the duration of Trypanosoma cruzi infection and the degree of humoral responsiveness.

Selective production of human antigen specific helper factor from normal volunteers: implications for human Ir genes

Based on previous systems for generating helper cells and factors from mouse spleen cell cultures, an in vitro system for the production and detection of human helper factors to the synthetic polypeptide antigens (T,G)-A--L and GAT10 was developed. The factors are made by human peripheral blood leucocytes and are antigen-specific, as judged both by functional criteria and specific binding and elution from antigen columns. Out of the first six volunteers studied two were high responders to (T,G)-A--L, but non-responders to GAT, two responders to GAT but not (T,G)-A--L. One subject made factors to both antigens and the sixth reacted to neither. The antigens chosen are known to be under MHC-linked immune response (Ir) gene control in all animal species tested, with some strains being responders while others are not. The selective responsiveness, different between individuals, thus suggests that the response to these antigens in man is under Ir gene control. Because of the small size of the sample initially studied and HLA typed, it was not surprising that there was no clear-cut association of response with any particular histocompatibility type at the HLA-A, B, C or D locus.

Activation of human B lymphocytes (the in vitro polyclonal B cell activator-induced plaque-forming cell system)

The characteristics of human B lymphocyte triggering, differentiation, and regulation are described using the polyclonally induced anti-sheep red blood cell hemolytic plaque-forming cell assay system. Technical and methodologic considerations, cellular requirements and mechanisms of regulation including suppressor and helper influences are discussed. Also considered are theoretical concepts regarding normal immune response versus pathologic immune states and the potential biologic role of polyclonal activation in these human immune mechanisms.

Antigen-specific suppressor factors produced by T cell hybridomas for delayed-type hypersensitivity

This study describes the generation of T hybridoma lines which secret factors specifically suppressing delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC). AKR strain-derived T lymphoma BW 5147 cells were fused with spleen cells from mice primed with SRBC and containing antigen-specific T suppressor cells for DTH. Supernants from the derived hybridomas were tested for suppression of either expression of induction of DTH to SRBC. Six lines produced specific suppressor activity for the expression of DTH; 4 lines produced suppressor activity for the induction of DTH of which only one line was antigen-specific. These lines were passaged in normal AKR mice, and the serum obtained had activity up to 10(-4) dilution. The factor was effective across the H-2 barrier.

Induction of human antibody responses in vitro with emphasis on allogeneic helper factors

Systems have been developed for the reproducible production of antigen-specific plaque forming cells for both tonsillar and peripheral blood B cells. Allogeneic helper activity was an essential supplement and monocyte removal was important, especially in the peripheral blood situation. Highly active allogeneic helper factors could be obtained from undirectional MLC supernatants which aided the proeuction of antigen-driven plaques. These factors also caused a polyclonal activation of B lymphocytes. A number of clinical applications of the above system were described. A defect in the T cells of patients with chronic lymphocytic leukemia with respect to the generation of helper activities was delineated.

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.

Induction of human antigen-specific and non-specific helper factors in vitro

Human peripheral blood leucocytes, cultured for 4--6 days with the appropriate concentration of protein or synthetic polypeptide antigen, yield helper cells. These cells, after a further 24 hr incubation with the appropriate antigen release helper factors, which are of two types, antigen specific and non-specific; a similar situation to that described in the mouse. These factors are assayed by their effects on the plaque-forming cell response of mouse spleen cells cultures in vitro. The potential applications of this new assay for human T cell function are discussed.

Induction of plaque-forming cells in human blood lymphocytes cultured in the presence of antigen and Epstein-Barr virus: a study with normal donors and infectious mononucleosis patients

Normal human peripheral blood lymphocytes, stimulated in vitro with SRBC in the presence of Epstein-Barr virus (EBV), gave rise to plaque-forming cells (PFC) specific for the antigen. PFC levels were very low before day 4 and increased thereafter, reaching a maximum around day 8. However, the kinetics of the response varied considerably from donor to donor and from experiment to experiment. In some instances a second peak of PFC was obtained beyond day 10. Large differences in the magnitude of the response were observed among different normal donors, the overall responsiveness range covering four orders of magnitude. Peripheral blood lymphocytes from infectious mononucleosis patients in the acute stage of the disease, when a high titre of heterophil and anti-EBV antibodies were present, did not give rise to PFC. A return to normal responses was observed during recovery from the disease.

Hemolytic plaque formation to allogeneic human type A and B red cells

Plaque-forming cells can be generated from peripheral blood lymphocytes provided that the lymphocytes are prestimulated by in vitro sensitization in the presence of pokeweed mitogen. Of 91 blood type O persons whose lymphocytes were stimulated with red cell A antigen, 52% responded with plaque formation, whereas of 40 type O persons whose lymphocytes were stimulated with red cell B antigen, only 20% produced plaques. Similarly, reciprocal stimulation of type A and B persons showed higher plaque formation (65%) when 23 type B persons were stimulated with A than when 48 type A persons were stimulated with B red cells (19%). An optimal dilution of sensitizing cells is necessary and maximum time of sensitization was approximately 7 days.

Induction of haemolytic plaque-forming cells with sheep lymphoid cells in vitro

The in vitro induction of specific primary and secondary immune responses in sheep lymph node cell suspensions is described and suitable culture conditions determined. The induction of primary immune responses required supplementation of the culture medium with antigen-absorbed homologous serum or lymph, whereas the requirements for the induction of a secondary response were less stringent. The addition of 2-mercaptoethanol to the medium was required. The amounts of heterologous erythrocytes used for immunization were critical and optimal responses were obtained when 50 microleters of a 1% suspension were added to 1 ml cultures. Lymphocyte densities of about 5 X 10(6)/ml were found optimal in primary immune responses in vitro. Less than 2 X 10(6) cells/ml rarely gave rise to plaque-forming cell (PFC) generation, whereas densities of 10 x 10(6) and above reduced the number of PFC obtained per number of cultured cells. Lymphocytes obtained from the efferent lymph draining lymph nodes previously immunized with heterologous erythrocytes were found to generate PFC in vitro when specific antigen was added to the cultures, but attempts to generate PFC in vitro with cells from efferent lymph draining non-immunized nodes failed.

Marmoset species variation in the humoral antibody response: in vivo and in vitro studies

A comparison of the in vivo and in vitro antibody response capabilities of two marmoset species, Saguinus fuscicollis and Saguinus oedipus oedipus, revealed the former to be superior in elaborating humoral antibody. In vivo challenges with Escherichia coli lipopolysaccharide (LPS) and Salmonella typhi flagella consistently yielded higher antibody titres in S. fuscicollis; indeed, with LPS antigen, multiple inoculations of S.o. oedipus marmosets led ultimately to a decrease in antibody formation, in contrast to the anamnestic response of S. fuscicollis. This species differential in immune competence was also suggested in the in vitro stimulation of peripheral blood leucocytes (PBL) and spleen cells with sheep red blood cells (RBC). None of 55 S.o. oedipus PBL cultures and 49 of 89 (55%) S. fuscicollis cultures responded to the test antigen. A similar differential in response to sheep RBC was noted with the spleen cells of each species, although this report contrasts the antibody-forming potential of two marmoset species, a comparison of the immunological response profile of marmosets to those of other laboratory animals challenged with similar antigens suggests these primates may be relatively incompetent. The possible relationship between the haemopoietic chimerism of marmosets and a diminished immune competence is discussed.

Primary in vitro antibody formation in the rat: partial characterization and properties of an inhibitor cell present in normal spleen

Rat spleen cells are shown to be unresponsive to sheep red cells (SRBC) in vitro under conditions in which thoracic duct lymphocytes (TDL) respond very well. By adding unresponsive spleen cells to responsive TDL cultures, the spleen cells are shown to contain an inhibitor capable of preventing the response to SRBC. The inhibitory activity is a property of live cells; it is sensitive to radiation doses as low as 100 R x rays and to mitomycin C. It can be completely removed from spleen cell suspensions by extraction with large amounts of carbonyl iron or by filtration through nylon wool columns. It is less efficiently removed by filtration through Sephades G-10 columns, and is completely resistant to the cytotoxic effects of silica. From a practical point of view, extraction of a spleen cell suspension with carbonyl iron is a useful method of obtaining fully responsive lymphocyte populations from rat spleen.

Detection of acceptor sites on human lymphocytes for antigen-specific T cell factors

Mouse antigen-specific T cell factors are absorbed by human peripheral blood lymphocytes at acceptor sites. The acceptors are products of HLA-linked genes, which may be human immune response genes.

Antibody formation by human tonsil cells in vitro

The ability of human tonsil lymphocytes to give an anti-SRBC response in conventional cultures and in microcultures was studied. It was found that about two-thirds of tonsils responded with a significant number of plaque-forming cells (PFC), and that in some instances the response could be augmented if allogeneic tonsil cell (irradiated or intact) were added. Moreover, tonsil lymphocytes which failed to give a response on their own often responded upon addition of an appropriate number of allogeneic tonsil cells. The response was remarkably improved if allogeneic tonsil supernatant or conditioned medium were added. An anti-SRBC response was also obtained if SRBC was omitted from the cultures. The frequency of anti-SRBC specific B cells was estimated as 1/60000 (f = 1-7 X 10(-5)).