Specific in vitro antimannan-rich antigen of Candida albicans antibody production by sensitized human blood lymphocytes

Induction of antibody forming cells with specificity for Candida albicans mannoproteins in cultures of human peripheral blood lymphocytes

A method is described for the induction of a specific antibody response to Candida albicans in cultures of normal human peripheral blood lymphocytes (PBL). PBL were cultured in the presence of whole C. albicans cells and the antibody response was evaluated by the ELISPOT technique, on plastic wells coated with a purified candidal cell well mannoprotein (MP). Under the conditions described here, a specific antibody response was obtained in all of the eight donors tested. The response was antigen-dependent and antigen-specific, peaked around day 10-12 of culture and the antibodies belonged to both the IgM and the IgG isotypes. By testing the cultured cells on MP from different Candida species, the method permitted the detection of antibodies directed against MP epitopes shared by C. albicans and C. parapsilosis.

Induction by anti-CD40 antibody or soluble CD40 ligand and cytokines of IgG, IgA and IgE production by B cells from patients with X-linked hyper IgM syndrome

We studied the ability of B lymphocytes from patients with X-linked hyper IgM syndrome (HIGM1) to be activated via the CD40 membrane receptor. HIGM1 is caused by a CD40 ligand gene mutation, leading to defective expression on the membrane of activated T lymphocytes. We found that triggering of B cells by an anti-CD40 monoclonal antibody or the soluble CD40 ligand plus interleukin (IL)-4 or IL-10 led to B cell proliferation and/or differentiation towards IgG, IgA and IgE secretion. This was reflected by transcription of C gamma, alpha and epsilon membrane isotype expression and IgG, IgA and IgE production. These results confirm the integrity of B cells in patients with the HIGM1 immunodeficiency and open up new therapeutic possibilities.

Spontaneous IgM autoantibody production in vitro by B lymphocytes of normal human neonates

Human neonate B lymphocytes display unique phenotypic and functional characteristics: in addition to CD1c antigens, CD5+ and CD5- subsets both express activation markers such as CD23 and Bac-1. They proliferate strongly in the presence of various lymphokines (rIL-2, rIL-4, low molecular weight BCGF), but differentiate poorly in the presence of the same lymphokines, pokeweed mitogen and Epstein-Barr virus. It has also been reported that human neonate B lymphocytes produce polyreactive autoantibodies after in vitro activation by Staphylococcus aureus Cowan I and transformation by Epstein-Barr virus. We now show that, in the absence of in vitro stimulation, human neonate B lymphocytes produce polyreactive antibodies of the IgM isotype against several autoantigens. The B lymphocytes involved expressed membrane IgD, IgM, CD23 and CD11b molecules; CD5 expression was variable. This phenotype was consistently found on a minority of B lymphocytes and is similar to that of polyreactive autoantibody-producing B cells in mice. We also found that autoantibody production in vitro could occur in the absence of any T helper effect. The function of these autoantibodies is not clearly established, but their occurrence in a large proportion of human neonates strongly suggests that they play an important role in the development of the immune system.

Selective IgG subclass deficiencies and antibody responses to pneumococcal capsular polysaccharide antigen in adult community-acquired pneumonia

We measured the serum concentrations of IgG subclasses in healthy subjects (n = 26) and in patients with community-acquired pneumonia (CAP) on admission (n = 38), at recovery (n = 21), and 9 months after admission (n = 19). Then, in 8 of the control subjects and 15 of the patients, we measured IgG subclasses and mean serum antibody concentrations of pneumococcal capsular polysaccharides before and 3 wk after immunization with a pneumococcal vaccine. Compared to the control subjects, the serum concentration of the IgG2 subclass was lower at admission in patients with CAP of bacterial or unknown cause (p less than 0.005). Concentrations of IgG subclasses in patients did not differ between admission and recovery, or between admission and 9 months later. After vaccination, in both control subjects and patients, there was an increase in the concentrations of IgG2 subclasses (p = 0.01) and antipneumococcal antibodies (p less than 10(-4)). We show that serum IgG2 concentration in patients with CAP of bacterial or unknown cause is lower than in healthy subjects and remains lower for several months. After immunization with a pneumococcal vaccine, the increase in serum concentrations of IgG subclasses and antipneumococcal antibodies in patients does not differ from those in control subjects.

Characterization of Candida albicans mannan-induced, mannan-specific delayed hypersensitivity suppressor cells

We have shown previously that CBA/J mice immunized with Candida albicans developed delayed hypersensitivity (DH) demonstrable with mannan (MAN) extracted from the same organism and that the intravenous (i.v.) injection of MAN prior to or during the immunization phase resulted in the suppression of the MAN-specific DH response. In this study, we demonstrate that MAN-induced suppression of DH is a T-lymphocyte-mediated phenomenon. Suppressor cells induced in vivo by the i.v. injection of MAN into naive mice 1 to 7 days prior to harvest were passaged through nylon wool, treated with various surface-specific antibodies and complement, and then injected i.v. into immunized syngeneic recipients. Enrichment of splenic T cells by passage over nylon wool and transfer of the nylon-wool-nonadherent populations to immunized recipient mice suppressed DH in a dose-dependent manner. Depletion of Thy+ or Lyt-2+ cells from nylon-wool-nonadherent populations regularly ablated the ability of such suspensions to transfer suppression. Treatment of the same transfer suspensions with anti-Lyt-1 had variable effects, suggesting that the surface density of the Lyt-1 antigen was not as constant from population to population as was the Lyt-2 antigen. In addition, C. albicans MAN-induced suppressor cells were able to suppress DH demonstrable with Candida tropicalis MAN in animals immunized with C. tropicalis. Suppression of DH by MAN in this model, therefore, is mediated by Thy+ Lyt-2+ lymphocytes.

Candida albicans: mannan and protein activation of cells from various human lymphoid organs

Challenging human lymphocytes with soluble cytoplasmic Candida albicans protein antigen (CP) and cell-wall-derived C. albicans mannan (CM) induced DNA synthesis and antibody secretion measured as plaque-forming cells (PFC) in an indirect haemolytic assay. Enriched T and B lymphocytes responded poorly to CP and CM. However, when adherent cells were added, T and B cells responded well to CM, but not to CP. Peripheral blood lymphocytes responded more strongly to CP than to CM, with peak stimulation on day 7. Bone marrow cells displayed similar DNA synthetic responses as blood lymphocytes, but peak stimulation occurred on days 4 and 5 for CP and CM, respectively. Cells from the various parenchymal organs, including adenoid, tonsil, and spleen, showed peak DNA synthesis ranging from days 3 to 5 with a tendency for CM to produce an earlier response than CP. In contrast to that observed in blood and bone marrow cells, CM induced a higher DNA synthesis in cells from parenchymal organs than CP, which gave low stimulations. PFC, like DNA synthesis, in blood and bone marrow cells responded best to CP, whereas spleen cells showed the highest response to CM. In blood and bone marrow cells, only IgG PFC were induced, but in spleen cells IgA and IgM PFC were also stimulated by CM. Fetal liver cells responded poorly to these two Candida preparations. CM but not CP stimulated DNA synthesis in umbilical cord blood lymphocytes and IgG, IgA, and IgM in spleen cells, suggesting that CM is a polyclonal activator and that CP acts as an antigen.

Direct activation of human B lymphocytes by Candida albicans-derived mannan antigen

We have studied the activation of human resting B cells by a carbohydrate antigen, mannan, with a polymannose branched repetitive structure. Mannan has been extracted from the cell wall of the Candida albicans yeast. For this purpose, dense G0 B lymphocytes were purified from tonsils. Mannan antigen was shown to trigger B cell activation, since an increase of cell volume and RNA synthesis occurred. B cell proliferation was observed following addition of recombinant interleukin 2, but not following addition of recombinant interleukin 4 or low-molecular-weight BCGF. The B cell activation appears to be mannan-specific since B cells obtained from mannan-sensitized subjects but not from unsensitized subjects were responsive. The observation that mannan antigen can directly activate specific dense B lymphocytes can be related to the previous observation that the in vitro anti-mannan antibody production does not require a cognate T-B cell interaction.

Mannan as an antigen in cell-mediated immunity (CMI) assays and as a modulator of mannan-specific CMI

Mannan (MAN) extracted from Candida albicans 20A was investigated for its potential as an antigen in the detection of cell-mediated immunity (CMI) in vivo and in vitro and for its ability to modulate CMI when administered intravenously (i.v.). CBA/J mice were either immunized as adults by the cutaneous inoculation of 10(6) viable blastoconidia or colonized as infants (primed) and then boosted cutaneously as adults. When immunized animals were footpad tested with MAN, highly significant delayed-type hypersensitivity (DH) responses were detected. The DH responses to MAN were of a greater magnitude than those noted with the same quantity of cell wall glycoprotein (GP), an ethylenediamine extract of the cell wall which contains both glucan and MAN. In contrast, GP was a better antigen for the detection of CMI responses in an in vitro lymphoproliferative assay with either spleen or lymph node cell suspensions. Mice treated with MAN i.v. prior to the initiation of immunization or between priming and secondary inoculations developed significantly suppressed DH reactions when tested with either MAN or GP. The lowest effective dose of MAN was 250 micrograms, maximum suppression occurred with 500 micrograms, and either dose given 1 week prior to immunization was suppressive. The suppression by MAN was specific for MAN or the MAN-containing GP. Responses to another unrelated candidal antigen, a membrane extract designated BEX, were relatively unaffected. MAN, therefore, was an effective antigen for the detection of CMI in vivo, and its administration i.v. created what appeared to be a MAN-specific suppression since it could be detected with both MAN and a MAN-containing extract from the cell wall. Caution must be exercised in the interpretation of these data, however, since the protein component of each of these extracts has not been characterized with respect to its potential role in the phenomena observed.

Activation of genetically major histocompatibility complex (MHC) class II-deficient B lymphocytes

It has been suggested that MHC class II molecules can transduce signals required for B-cell activation. Enhancement or inhibition of B-cell stimulation by anti-MHC class II molecule antibodies has likewise been reported. The study of B cells from patients with a combined immune deficiency due to a defective expression of MHC class II genes provides a useful tool for approaching the functional role of B-cell HLA class II molecules. We have thus analyzed the specific and nonspecific, cognate and noncognate B-cell activation of genetically HLA class II-deficient lymphocytes. B lymphocytes from 14 tested patients were able to synthesize RNA following stimulation with ionomycin and phorbol myristate acetate or anti-mu antibodies and with mannan, a T cell-independent polysaccharidic antigen. They were also able to synthetize DNA following the addition of ionomycin and PMA or of anti-mu antibodies in the presence of recombinant interleukin 2. Pokeweed mitogen failed to induce B-lymphocyte terminal differentiation into immunoglobulin-producing cells in the presence of normal T lymphocytes, while a combination of anti-CD2 antibodies were capable of triggering IgG synthesis. B-cell activation, whatever the condition used, did not induce HLA class II expression. Mannan-specific T cell-dependent antibody production (IgM) was detected in 6 of 14 patients. Anti-influenza virus antibody production was always found absent. These results are compatible with the hypothesis that B-cell activation events that do not require a cognate interaction with T cells can occur in the absence of HLA class II molecule expression, while the absence of HLA class II molecule expression prevents T-B cognate interaction.

Candida cell wall mannan: a polysaccharide with diverse immunologic properties

It is clear that mannan has the potential to influence multiple biologic functions in vivo and in vitro, including both mannan-specific and mannan-nonspecific activities. Based on in vitro studies, various mechanisms have been proposed for the regulatory activities observed, ranging from interference with normal PMNL and monocyte function to the induction of T suppressor cells. It may well be, in fact, that different mechanisms function at different levels depending upon the specific phenomenon being influenced. Approaches to determining the mechanisms involved in these regulatory phenomena, however, have been complicated by the fact that many studies were performed with mannan extracted in the laboratory by traditional methods and used as such without further purification. Most laboratory-acquired mannans appear to be heterogeneous mixtures containing polymers of differing size and charge. When such mixtures have been separated on the basis of size or charge, it has been shown that biologic function can be correlated with individual fractions, and that a single bulk preparation of mannan can contain components with opposing biologic activities. Resolution of the specific mechanisms involved in the regulatory phenomena described, therefore, will not be complete until homogeneous preparations of mannan are employed to investigate the mechanisms.

Actinobacillus actinomycetemcomitans in the pathogenesis of human periodontal disease

The present report reviews data implicating Actinobacillus actinomycetemcomitans in the etiology of human periodontal disease. Recent data are also presented relative to: (1) serological studies of this microorganism using monoclonal antibodies and the serodiagnosis of A. actinomycetemcomitans infections; (2) characterization of the serotype antigens; (3) studies of the serotype distribution of A. actinomycetemcomitans in extra-oral infections; and (4) examination of the correlation between A. actinomycetemcomitans colony morphology and fimbriae.

The effect of RU 41740 on the in vitro maturation of human B-cells

We have tested the effect of a Klebsiella pneumoniae extract, RU 41740, and its lipopolysaccharidic fraction (LPS-LAP) on the in vitro activation of human B-cells. Two models have been used: the polyclonal activation induced by pokeweed mitogen and the specific antibody production to mannan, a polysaccharide extracted from the cell wall of Candida albicans. We have shown that RU 41740, and especially its lipopolysaccharidic fraction, significantly increases the production of immunoglobulins and specific antibodies. This effect is mediated by T-lymphocytes, since preincubation of isolated T-cells, but not of non-T-cells, resulted in the same effect. Together with the known enhancing effect of LPS-LAP on T-cell proliferation, these data strongly suggest that LPS-LAP increases the production of B-cell-activating lymphokines by T-cells.

Mannan-specific and mannan-induced T-cell suppressive activity in patients with chronic mucocutaneous candidiasis

We have studied T- and B-cell responses to antigens of Candida albicans in 18 patients suffering from chronic mucocutaneous candidiasis. We have shown that in vitro production of antibody to one of these antigens, mannan, was absent during the active phase of the disease and that this absence was consequent to the activation of specific CD8(+) and CD8(-) suppressor T lymphocytes. Such activation was also observed when control T lymphocytes were incubated in the presence of monocytes and a high concentration of mannan. This suppressive effect was specific to antigens of Candida albicans, was radiosensitive, and was not consequent to the secretion of prostaglandin E2. It appeared as well that the induction of these suppressor T cells was HLA-DQ restricted. The suppressor T-cell activity induced by antigens of Candida albicans in vitro is thus comparable to the suppressor T-cell activity observed in vivo in patients affected with chronic mucocutaneous candidiasis. Defective handling of mannan by monocytes could result in the accumulation of mannan, resulting in the activation of specific T suppressor cells and in the consequent cellular immunodeficiency specific to Candida albicans. Successful treatment of the candidiasis resulted in complete correction of the immune abnormalities.

Specific binding of antigen onto human T lymphocytes

Human T lymphocytes sensitized to Candida albicans (CA) were shown to proliferate in cultures induced with mannan, a ramified polysaccharide extracted from the cell well of CA. We presently describe that, when we used strongly labeled [3H]mannan, antigen-specific T blast cells were able to bind the labeled mannan on their membrane. The observations that irrelevant blast cells did not bind [3H]mannan, and that mannan-specific blast cells did not bind tritiated pneumococcal polysaccharide SIII, indicate the specificity of mannan binding. Mannan binding was reversible and saturable. Mannan binding on T blast cells was inhibited by preincubation with monoclonal antibodies to T3 but not to other T cell-related molecules. The characteristics of this receptor suggest its identity with the T cell receptor for antigen. The direct binding of mannan could be either due to a cross-linking of the receptor by multivalent mannan or to a recognition of mannan in association with HLA-DQ molecules, as suggested by partial blocking of mannan binding using anti-HLA-DQ monoclonal antibodies.

Restriction of the in vitro anti-mannan antibody response by HLA-DQ molecules

In humans, the in vitro antibody response directed towards mannan, a polysaccharide extracted from the cell wall of Candida albicans, has been previously shown to be dependent on the presence of T lymphocytes and monocytes. Evidence is now given for the existence of a genetic restriction governing this response since antibody production is achieved provided that monocytes and T lymphocytes on one side and monocytes and B lymphocytes on the other side are of the same origin. In order to delineate the restriction element governing these interactions, blocking experiments have been designed using well-defined monoclonal antibody, anti-HLA class II molecules. The results clearly indicate that the restriction element belongs to the HLA-DQ molecular series, as shown in T-cell proliferation and antibody production assays in the presence of either T cells or T-cell supernatants. Incubation of isolated cell populations (T, B lymphocytes and monocytes) with the monoclonal antibody have indicated that DQ determinants are involved in the mannan presentation by monocytes to T and B cells. The HLA-DQ mediated restriction of the in vitro immune response to mannan has been observed in all the subjects tested, suggesting that mannan epitopes are preferentially, or even only, recognized in association with an unique group of HLA-class II molecules, namely HLA-DQ.

HLA class II restriction governing cell cooperation between antigen-specific helper T lymphocytes, B lymphocytes and monocytes for in vitro antibody production to influenza virus

To study HLA class II compatibility requirement for in vitro antibody production to influenza virus, semipurified T lymphocytes, B lymphocytes and monocytes from HLA-typed responder donors were used. The presence of the three subpopulations was required for antibody production while a mixture of only two of those was ineffective. When using fresh T lymphocytes which exert an allogeneic suppressive effect and may also exhibit allogeneic helper activity, it was not possible to conclude an HLA class II-linked restriction of T-B cell cooperation although there was a suggestion of it. However, a grown H3 hemagglutinin-specific T cell line (L2), previously shown to be restricted by HLA-DR molecule (DR1) for interaction with antigen-presenting cells and devoid of allogeneic reactivity, exerts an HLA class II-restricted helper activity. This was demonstrated by various combinations of HLA-DR semi-compatible or incompatible B lymphocytes and/or monocytes with L2 T cells. The restriction element was identified as an HLA-DR determined since HLA-DC-compatible, HLA-DR-incompatible B lymphocytes were not helped by L2 T cells. In addition, monoclonal anti-HLA-DR but not anti-HLA-DC antibodies directed to the relevant specificity did inhibit the antigen-specific helper activity. We present evidence that not only T monocyte but also T-B and/or T-B-monocyte interactions are HLA class II restricted.

A purified polysaccharide isolated from Candida albicans induces antibody response in vitro by human peripheral blood lymphocytes and discriminates between sera from normal and Candida albicans-infected individuals

A purified polysaccharide extracted from Candida albicans (MPPS), stimulates in vitro synthesis of specific antibodies by human peripheral blood lymphocytes. These antibodies can be detected by a sensitive enzyme-linked immunoassay. The same assay can be applied to the quantitation of anti-candida antibodies in serum. Statistically significant differences were found between sera of normal and candida-infected individuals.