Increase of lymphocytes with Fc receptors for IgE in patients with allergic rhinitis during the grass pollen season

Priming of the Nose and Eustachian Tube during Natural Pollen Exposure

Previous studies have suggested that seasonal allergen exposure in allergic individuals “primed” or increased the response of nasal mucosa to subsequent allergen challenge. The purpose of this study was to document the specificity of nasal “priming” and to determine if this effect extends to the eustachian tube (ET). Eight subjects with ragweed allergic rhinitis were challenged intranasally with increasing doses of ragweed (0.05, 0.125, 0.25, 0.5, 2.5, and 5.0 mg) and histamine (0.01, 0.1, 0.5, 1.0, 5.0, and 10 mg) before, during, and 4–6 weeks and 3–5 months after ragweed season. Nasal conductance and ET function were evaluated by computerized posterior rhinomanometry and sonotubometry, respectively. The dose that decreased nasal conductance below a threshold value of 0.1 L/sec/cm H2O was defined as the nasal obstructing (NO) dose and that which resulted in an inability to open the ET by swallowing was the ET obstructing (ETO) dose. For ragweed and histamine mean NO doses decreased during and up to 6 weeks after ragweed season compared to preseason and 3–5 months postseason doses. The ETO doses showed similar patterns for histamine challenges, but ET hyperresponsiveness to ragweed was limited to the ragweed season. Patients’ responses did not correlate with serum IgE antibody level. These data show that both the nose and ET can be primed by allergen exposure to manifest heightened responses to both specific allergen and a nonspecific substance.

Current overview of allergens of plant pathogenesis related protein families

Pathogenesis related (PR) proteins are one of the major sources of plant derived allergens. These proteins are induced by the plants as a defense response system in stress conditions like microbial and insect infections, wounding, exposure to harsh chemicals, and atmospheric conditions. However, some plant tissues that are more exposed to environmental conditions like UV irradiation and insect or fungal attacks express these proteins constitutively. These proteins are mostly resistant to proteases and most of them show considerable stability at low pH. Many of these plant pathogenesis related proteins are found to act as food allergens, latex allergens, and pollen allergens. Proteins having similar amino acid sequences among the members of PR proteins may be responsible for cross-reactivity among allergens from diverse plants. This review analyzes the different pathogenesis related protein families that have been reported as allergens. Proteins of these families have been characterized in regard to their biological functions, amino acid sequence, and cross-reactivity. The three-dimensional structures of some of these allergens have also been evaluated to elucidate the antigenic determinants of these molecules and to explain the cross-reactivity among the various allergens.

Evidence of a novel allergenic protein Narcin in the bulbs of Narcissus tazetta

Several plant-derived allergens have been identified which result in the formation of immunoglobulin E antibodies. Primarily, these allergens belong to the protein families including seed storage proteins, structural proteins and pathogenesis-related proteins. Several allergens are also reported from flower bulbs which cause contact dermatitis. Such symptoms are highly common with the bulb growers handling different species of Narcissus. Narcissus toxicity is also reported if the bulbs are consumed accidentally. The present study aimed to characterize the protein from the bulbs of Narcissus tazetta responsible for its allergenic response. A 13 kDa novel allergenic protein, Narcin was isolated from the bulbs of Narcissus tazetta. The protein was extracted using ammonium sulfate fractionation. The protein was further purified by anion exchange chromatography followed by gel filtration chromatography. The N-terminal sequence of the first 15 amino-acid residues was determined using Edman degradation. The allergenicity of the protein was measured by cytokine production using flow cytometry in peripheral blood mononuclear cells. Further estimation of total IgE was performed by ELISA method. This novel protein was found to induce pro-inflammatory cytokines and thus induce allergy by elevating total IgE level. The novel protein, Narcin isolated from Narcissus tazetta was found to exhibit allergenic properties.

Altered expression and action of the low-affinity IgE receptor FcepsilonRII (CD23) in asthmatic airway smooth muscle

BACKGROUND

Changes in cell surface expression of certain immunoglobulin Fc receptors have been demonstrated in leukocytes isolated from the lungs of atopic asthmatic individuals. This, together with emerging evidence that Fc receptors can also be expressed and activated in non-bone marrow-derived cell types, including airway smooth muscle (ASM), raises the hypothesis that the atopic asthmatic ASM phenotype is associated with an altered endogenous expression and action of specific Fc receptors present in the ASM itself.

OBJECTIVE

The current study addressed the above hypothesis by examining (1) whether the expression of certain key Fc receptor subtypes for IgE and IgG is altered in ASM tissue isolated from human atopic asthmatic individuals and (2) whether this altered Fc receptor expression is comparably induced in naive human ASM tissue and cultured cells after their passive sensitization with human atopic asthmatic serum or IgE immune complexes.

METHODS

Messenger RNA and cell surface protein expression of the individual IgG receptor subtypes FcgammaRI, FcgammaRII, and FcgammaRIII, as well as the IgE receptor subtypes FcepsilonRI and FcepsilonRII, were examined in human ASM tissue isolated from atopic asthmatic and control (nonatopic/nonasthmatic) individuals. In addition, we examined the effects of passive sensitization of ASM tissue and cultured ASM cells with control serum, atopic asthmatic serum, or exogenously administered IgE immune complexes on Fc receptor expression and action (ie, induction of proinflammatory cytokine release).

RESULTS

The observations demonstrate that (1) human ASM tissue expresses messenger RNA and surface protein for FcepsilonRII, as well as for all the Fcgamma receptor subtypes, (2) in contrast to unaltered Fcgamma subtype expression, however, relative to control human ASM, FcepsilonRII is significantly up-regulated in inherently asthmatic ASM tissue, (3) up-regulated expression of FcepsilonRII represents, at least in part, an inducible phenomenon that is largely attributed to IgE immune complex-coupled activation of the receptor, and (4) the latter action is associated with FcepsilonRII-induced autologous elaboration of the proinflammatory cytokine, IL-1beta, by the atopic sensitized ASM.

CONCLUSION

These observations provide new evidence that human ASM tissue expresses FcepsilonRII in addition to all 3 subtypes of Fcgamma receptors and that the expression of FcepsilonRII is selectively increased in atopic asthmatic ASM, a phenomenon associated with IgE immune complex/FcepsilonRII-mediated elaboration of IL-1beta by the ASM itself.

Hyposensitization to allergic reaction in rDer f 2-sensitized mice by the intranasal administration of a mutant of rDer f 2, C8/119S

C8/119S is a mutant of recombinant Der f 2 (rDer f 2), and lacks a disulphide bond possessed by wild-type rDer f 2. In humans and mice, C8/119S has a very weak IgE-binding capacity compared with the wild-type, but possesses a T cell reactivity comparable to that of the wild-type. C8/119S may thus be a safe immunotherapeutic agent for house dust mite allergy. The aim of the present study was to evaluate whether the intranasal administration of C8/119S could suppress an immediate allergic reaction in mice sensitized with wild-type rDer f 2, possessing an allergic activity comparable to native counterparts purified from mite extract. Seven-week-old male A/J mice were immunized with wild-type rDer f 2 four times, and then intranasally administered 0.2-2 microg of wild-type, 0.2-20 microg of C8/119S, or PBS alone, three times a week for 4 weeks. Seven days after the last administration, the mice were examined for an immediate allergic reaction. The animals administered 2 microg of C8/119S (C2.0 group) showed significantly reduced immediate bronchoconstriction provoked by the i.v. injection of 1 and 10 microg of wild-type rDer f 2, compared with the PBS-treated mice. Similar results were obtained when we examined mice 10 weeks after the last administration. The reactions in the other groups given wild-type or C8/119S also tended to decrease in severity in comparison with the animals of the PBS group. The allergic phenotypes of the T cells, B cells, and basophils in the C2.0 group were shifted to that of naive mice without immunization. We conclude that C8/119S has hyposensitizing activities in mice sensitized with wild-type rDer f 2. C8/119S may be useful for immunotherapy of house dust mite allergy.

Autologously up-regulated Fc receptor expression and action in airway smooth muscle mediates its altered responsiveness in the atopic asthmatic sensitized state

To elucidate the role of IgE-dependent mechanisms in inducing altered airway responsiveness in the atopic asthmatic state, the expression and actions of Fc receptor activation were examined in isolated rabbit tracheal smooth muscle (TSM) tissue and cultured cells passively sensitized with sera from atopic asthmatic patients or nonatopic/nonasthmatic (control) subjects. Relative to control tissues, the atopic asthmatic-sensitized TSM exhibited significantly increased maximal isometric contractility to acetylcholine (P < 0. 01) and attenuated maximal relaxation responses and sensitivity (i.e.,-log ED50) to isoproterenol (P < 0.005). These changes in agonist responsiveness in atopic sensitized TSM were ablated by pretreating the tissues with a blocking mAb to the low affinity receptor for IgE, FcepsilonRII (i.e., CD23) or by depleting the sensitizing serum of its immune complexes. Moreover, in complimentary experiments, exogenous administration of IgE immune complexes to naive TSM produced changes in agonist responsiveness that were qualitatively similar to those obtained in the atopic asthmatic-sensitized state. Extended studies further demonstrated that, in contrast to their respective controls, atopic asthmatic serum-sensitized human and rabbit TSM tissue and cultured cells exhibited markedly induced mRNA and cell surface expression of FcepsilonRII, whereas constitutive expression of the IgG receptor subtype, FcgammaRIII, was unaltered. Finally, the up-regulated mRNA expression of FcepsilonRII observed following exposure of TSM to atopic asthmatic serum or to exogenously administered IgE immune complexes was significantly inhibited by pretreating the tissues or cells with anti-CD23 mAb. Collectively, these observations provide evidence demonstrating that the altered agonist responsiveness in atopic asthmatic sensitized airway smooth muscle is largely attributed to IgE-mediated induction of the autologous expression and activation of FcepsilonRII receptors in the airway smooth muscle itself.

Interleukin-4 and low-affinity receptor for IgE on B cells in peripheral blood of patients with atopic bronchial asthma

BACKGROUND

A greater frequency of type 2 helper cells producing IL-4 without interferon-gamma is thought to be responsible for the elevated IgE in serum of atopic subjects. However, the proportion of B cells responding to IL-4 by an increased synthesis of IgE is also higher in atopic subjects than in nonatopic subjects.

OBJECTIVE

Important questions are whether the elevated IgE in atopic subjects is due to overproduction of IL-4 by T cells, the enhanced sensitivity of B cells to IL-4, or both and whether functional alterations of T and B cells are related to the development of allergic diseases.

METHODS

Spontaneous and IL-4-induced CD23 expression on B cells was examined to evaluate the response of B cells to IL-4, and production of IL-4 by concanavalin-A-stimulated peripheral blood mononuclear cells (PBMCs) was measured to evaluate the T-cell function in nonatopic normal subjects, atopic normal subjects, and patients with symptomatic bronchial asthma.

RESULTS

IL-4-induced expression of CD23 on B cells was greater in normal atopic subjects and atopic patients with bronchial asthma than in normal nonatopic subjects. IL-4 generated by concanavalin A-stimulated PBMCs was also higher in normal atopic subjects and atopic patients with bronchial asthma than in normal non-atopic subjects. The expression of CD23 on B cells and IL-4 generation by concanavalin-A-stimulated PBMCs were not different between normal atopic subjects and atopic patients with bronchial asthma.

CONCLUSIONS

Both B-cell and T-cell functions are enhanced in atopic subjects. However, neither enhanced B-cell nor T-cell function is a hallmark in development of allergic diseases.

Seasonal variations of interleukin-4 and interferon-gamma release by peripheral blood mononuclear cells from atopic subjects stimulated by polyclonal activators

IgE synthesis is controlled by interleukin (IL)-4 and interferon (IFN)-gamma, but there is heterogeneity in the IL-4 response depending on the sensitization of patients and natural allergen exposure. In patients sensitized to various allergens, we studied the synthesis of IL-4, IFN-gamma, and IgE to determine to what extent their in vitro immune response may be influenced by pollen season, depending on their sensitization. We studied 12 nonallergic individuals, seven patients sensitized to cypress pollen, 12 sensitized to grass pollen, 14 sensitized to several pollens, and 42 patients with polysensitization. The release of IL-4 and IFN-gamma from peripheral blood mononuclear cells stimulated by polyclonal agents (calcium ionophore A23187 and phorbol myristate acetate) was measured by ELISA. The spontaneous and IL-4-induced release of IgE was measured by ELISA. In patients with cypress pollen allergy, IL-4 and IgE release were significantly lower than in patients with other allergies. In the pollen-sensitized group, IL-4 and IgE release were significantly higher during the pollen season than out of it. No variation in IL-4 or IgE release was observed in the polysensitized group. IFN-gamma production was not affected by the pollen season. These data show that the seasonal variations of IL-4 and IgE synthesis differ according to the sensitization of patients.

The effect of T-cell depletion on enhanced basophil histamine release after in vitro incubation with live influenza A virus

A number of mechanisms participate in virus-induced asthma. Previously, we described enhanced basophil histamine release (HR) during an experimentally induced rhinovirus infection and after in vitro incubation of peripheral blood mononuclear cells (PBMC) with influenza virus. This study extends our previous observations and examines the effect of influenza A virus on basophil leukotriene C4 (LTC4) release as well as the effect of T-cell depletion on virus-enhanced basophil HR. PBMC were isolated from ragweed-allergic subjects and incubated with live influenza A virus or control medium (allantoic fluid). After incubation with influenza A, ragweed antigen (AgE) stimulated LTC4 and HR were enhanced (P less than 0.05). To further define the role of T cells in virus-enhanced basophil secretion, PBMC were isolated and divided into two aliquots. In one aliquot, T cells were removed by magnetic bead separation of mouse monoclonal anti-CD3-coated lymphocytes. T-cell-depleted and nontreated PBMC suspensions were incubated with influenza A or control medium, collected, and challenged with AgE to release histamine. Basophil HR was enhanced in the virus-treated group of PBMC that had not undergone T-cell depletion. In contrast, virus incubation did not enhance HR in the T-cell-depleted fraction. Finally, preliminary analysis of the supernate from virus-treated leukocytes indicates the presence of interferon-gamma. These findings suggest that T cells, and their cytokine products, play an integral role in the process by which viruses enhance basophil HR.

Levels of serum IgE, serum soluble-Fc epsilon RII, and Fc epsilon RII(+) peripheral blood lymphocytes in atopic dermatitis

Levels of serum IgE, serum soluble-Fc epsilon RII (S-Fc epsilon RII), and Fc epsilon RII(+) peripheral blood lymphocytes (PBL) were examined in 73 patients with atopic dermatitis (AD) and 17 control subjects with no atopic disease, in order to investigate the correlation of these parameters with AD. AD patients showed increases in IgE, S-Fc epsilon RII and Fc epsilon RII(+)PBL as compared with control subjects. In AD patients, levels of serum IgE and Fc epsilon RII(+)PBL increased as the extent of dermatitis became more severe, while levels of serum S-Fc epsilon RII showed no correlation with the extent of dermatitis. In 8 of the 73 AD patients who showed an improvement in their symptoms with treatment with topical corticosteroids or antihistamine, IgE, Fc epsilon RII(+)PBL, and S-Fc epsilon RII were measured before and after treatment. Fc epsilon RII(+)PBL correlated with disease activity; IgE and S-Fc epsilon RII did not show any such correlation. Patients with elevated IgE levels (IgE greater than 5,000 U/ml) showed low levels of S-Fc epsilon RII. Severely affected cases with a history of respiratory atopy also showed decreased S-Fc epsilon RII levels. It is believed that S-Fc epsilon RII binds to IgE in serum and may neutralize or down-regulate IgE mediated allergic reactions. A low level of S-Fc epsilon RII may cause an elevation of IgE and an exacerbation of the disease.

Fc epsilon receptor II/CD23-positive lymphocytes in atopic dermatitis. I. The proportion of Fc epsilon RII+ lymphocytes correlates with the extent of skin lesion

Cells expressing Fc receptors for IgE (Fc epsilon RII) were identified in the peripheral blood from patients with atopic dermatitis and with eczematous dermatitis, and normal non-atopic subjects by using monoclonal antibodies to human lymphocyte Fc epsilon RII, and to lymphoid cell-surface antigens by immunofluorescence staining. Based on the extent of the dermatitis patients were classified as severe (greater than 50% skin surface involved), moderate (50-10%) and mild (less than 10%). Patients with severe and moderate atopic dermatitis had 5.9% and 5.7% Fc epsilon RII+ peripheral blood mononuclear cells (PBMC), respectively, that were significantly higher than percentages in mild atopic dermatitis patients (2.6%), severe to moderate eczematous dermatitis patients (2.3%), mild eczematous dermatitis patients (2.2%) and normal individuals (1.7%)(0.05 greater than P). In severe and moderate atopic dermatitis patients, 10% of Fc epsilon RII+ PBMC were T cells that preferentially expressed CD8, and the remainder B cells and monocytes. Fc epsilon RII+ T cells comprised 1% of peripheral T cells, while half or more of peripheral B cells expressed Fc epsilon RII. In mild atopic dermatitis patients, eczematous dermatitis patients and normal subjects. Fc epsilon RII were expressed exclusively on 25-35% of peripheral B cells. Short-term treatment and long-term follow-up of atopic dermatitis patients revealed that changes in the skin condition were related closely to fluctuations in the proportion of Fc epsilon RII+ PBMC. Total serum IgE levels and atopic respiratory allergy did not influence the percentage of Fc epsilon RII+ PBMC. These findings suggest that the percentage of Fc epsilon RII+ PBMC reflects the extent of atopic dermatitis.

The expression of IgE Fc receptors on lymphocytes of allergic patients

Peripheral blood lymphocytes from nonatopic subjects and atopic patients were analyzed for cells expressing Fc receptors for IgE (Fc epsilon R). Nonatopic humans and atopic patients in remission had approximately 1 percent of Fc epsilon R+ peripheral blood lymphocytes. Usually greater than 99 percent of these cells were mIgM+/mIgD+ B cells. However, in approximately 10 percent of nonatopic and atopic subjects a transient increase of Fc epsilon R+ lymphocytes to 3-6 percent was observed in the absence of any disease manifestations and measurable changes in the serum IgE level. At times of increased numbers of peripheral blood Fc epsilon R+ lymphocytes, up to 1 percent Fc epsilon R+ positive cells were detected in isolated T cell preparations. The Fc epsilon R+ T cells reacted with the monoclonal antibody Lyt 3 to the sheep erythrocyte receptor of human T cells but not the anti-T cell antibody OKT3, and fractions also with the monoclonal antibodies OKT8 (cytotoxic and suppressor T cells) and OKM1, which binds to an antigen present on monocytes and a subpopulation of T cells and large granular lymphocytes. No OKT4+ (helper T cells) Fc epsilon R+ cells were detected. The reactivity with monoclonal antibodies to T cell subsets of the Fc epsilon R+ T cells paralleled the reactivity of the IgG Fc receptor positive T cells. In contrast to patients with allergic rhinitis and asthma, patients with severe atopic dermatitis or the Hyper IgE Syndrome always had significantly elevated percentage of Fc epsilon R+ lymphocytes (4-10 percent), which were almost entirely B cells since less than 0.1 percent Fc epsilon R+ T cells were detected in these patients. Atopic dermatitis patients receiving systemic corticosteroid treatment had only 0.2 percent Fc epsilon R+ lymphocytes which was significantly less than the 1 percent of the nonatopic control donors. Attempts to define the function of Fc epsilon R on human B and T lymphocytes have been unsuccessful thus far; however, the increase of Fc epsilon R+ cells associated with atopic disease in man and parasitic infections in rats and mice suggest that Fc epsilon R+ lymphocyte may be involved in the IgE isotype regulation.

T and B lymphocytes with immunoglobulin E Fc receptors (Fc epsilon R) in patients with nonallergic hyperimmunoglobulinemia E: demonstration using a monoclonal antibody against Fc epsilon R-associated antigen

T and B cells bearing Fc receptors for IgE (Fc epsilon R) were studied in 7 patients with hyperimmunoglobulinemia E (2 with hyper IgE syndrome and 5 with Kimura's disease). Fc epsilon R was detected by both rosette formation with IgE-coated red cells (Eo'-IgE) and immunofluorescence assay using H107 monoclonal antibody recognizing a determinant(s) associated with lymphocyte Fc epsilon R. A high correlation was observed between the proportions of Eo'-IgE rosette-forming cells (RFC) and H107+ cells. All patients had a large number of Fc epsilon R-positive cells (mean +/- 1 SD; 9.7 +/- 3.7% Eo'-IgE-RFC, 8.4 +/- 3.4% H107+ cells) in contrast to those of 6 normal subjects (0.7 +/- 1.2% Eo'-IgE-RFC, 0.3 +/- 0.4% H107+ cells). In one patient with Kimura's disease, the presence of Fc epsilon R-bearing T cells was confirmed by two-dimensional flow cytometry, using fluorescein isothiocyanate (FITC)-H107 and phycoerythrin (PE)-Leu-1. H107 antigens seemed to be expressed on both helper/inducer and suppressor T-cell populations. The direct analysis of Fc epsilon R+ T cells by 2-D flow cytometry with H107 antibody may facilitate the study of hyperimmunoglobulinemia E.

Fc epsilon receptors on human cell lines and peripheral blood lymphocytes detected by binding of IgE immune complexes

To identify Fc epsilon receptors on human cell lines and peripheral blood lymphocytes, we developed a new method which relies on the binding of constructed immune complexes to Fc epsilon receptor-positive cells. Cell suspensions from either cell lines or peripheral blood lymphocytes were incubated with complexes of human myeloma IgE and murine monoclonal anti-human IgE at various ratios prior to cytocentrifugation. The complexes bound to the cells were subsequently visualized by immunoperoxidase staining. The specificity of this assay to detect cell surface Fc epsilon receptors was shown by the ability of human myeloma IgE to block the binding of the IgE complexes, resulting in unstained cells, whereas IgM, IgG, and IgA were unable to block the binding of the complexes (stained cells). This method is reproducible, allows quantification of a single sample at different times, and provides a record of the results. It can also be adapted to identify any cell surface receptor for which the ligand is known.

IgE Fc receptor positive T and B lymphocytes in patients with the hyper IgE syndrome

The percentages of peripheral blood lymphocytes (PBL), bearing Fc receptors for IgE (Fc epsilon R) and IgG (Fc gamma R) were determined in four patients with the hyper IgE syndrome by a rosette assay employing IgE and IgG coated fixed ox erythrocytes. The patients had 8 +/- 3% Fc epsilon R+ and 13 +/- 8% Fc gamma R+ PBL, compared to 1.2 +/- 1% Fc epsilon R+ and 17 +/- 4% Fc gamma R+ PBL for control donors. T cells were isolated by rosetting with neuraminidase treated sheep erythrocytes (EN). Indirect immunofluorescence with Lyt 3 monoclonal antibody (MoAb) to the sheep erythrocyte receptor, followed by rosetting for Fc epsilon R and Fc gamma R showed that the patients' T cells contained less than 0.1% Fc epsilon R+ and 1.4 +/- 0.2% Fc gamma R+ cells; T cells from the control subjects contained less than 0.1% Fc epsilon R+ and 11 +/- 4% Fc gamma R+ cells. The non-T (EN rosette depleted) cells of the patients included 56 +/- 18% sIgM+/sIgD+, 45 +/- 9% Fc epsilon R+ and 35 +/- 27% Fc gamma R+ cells. Indirect immunofluorescence with MoAb to IgM, IgD, and NK cells (antibody B73.1) followed by rosetting for Fc epsilon R and Fc gamma R, indicated that 92 +/- 2% of the Fc epsilon R+ cells and 9 +/- 7% of the Fc gamma R+ cells were B cells (mu+/delta+), while 3 +/- 4% of the Fc epsilon R+ and 30 +/- 23% of the Fc gamma R+ cells were NK cells (B73.1+). Thus, most of the Fc epsilon R+ non-T cells were B cells, and only a small fraction appeared to be NK cells. On the other hand, Fc gamma R+ B cells were outnumbered by Fc gamma R+ NK cells (B73.1+) by three to one. The data indicate that patients with the hyper IgE syndrome have increased numbers of Fc gamma R+ PBL, most of them being B cells, whereas their T cells contain less than 0.1% Fc epsilon R+ cells.

Increase of peripheral blood B cells with Fc receptor for IgA in patients with IgA nephropathy

A B-cell subset with Fc receptors for IgA (B alpha cells) has been observed in human peripheral blood. To investigate aberrations of B cells in a diseased state, the percentages of B alpha cells were enumerated in peripheral blood from patients with IgA nephropathy, which is characterized by preponderant deposition of IgA-dominant immune complexes in the glomerular mesangial area. The present study showed a significant increase in B alpha cells in peripheral blood from patients with IgA nephropathy but not in those with chronic proliferative glomerulonephritis without mesangial IgA deposition. Most Fc alpha R-bearing cells were observed in surface IgA bearing lymphocytes. No linear correlation was observed between the levels of serum IgA and the percentages of B alpha cells. The addition of aggregated IgA to cultures did not induce Fc alpha R-bearing B cells in vitro. It is postulated that B alpha cells might have some pathogenetic role in the development of IgA nephropathy and that some antigenic stimuli might play a role in the increase of peripheral blood B alpha cells in patients with IgA nephropathy.