Changes In Cell Surface Phenotype Research Articles

Cell Dissociation Techniques in Salamanders.

Cell dissociation is an important technique for the study of tissue phenotypes. The method chosen to harvest cells from solid tissues profoundly influences the types of cells recovered. Methodology also shapes any biases that are introduced that can act upon cell surface protein phenotypes or gene expression. Here we describe examples of cell surface phenotypic changes and typical yields, under 4 different isolation conditions (enzymatic/non-enzymatic), using the axolotl spleen, and the regenerating limb. We describe simple methods for evaluating the liberation of viable cells and the downstream characterization of cell diversity using a live-cell flow cytometry approach. Of note, the cellular composition of dissociated cells and surface antigen detection vary with each condition. TrypLE and "no enzyme" protocols give the highest surface marker expression, but poor liberation of non-immune cells in the blastema. Liberase-DH and Liberase-TL have alternative neutral proteases and both give acceptable dissociation of diverse cell types in the blastema. Liberase-TL provides the highest yield of all cell sizes and a larger non-immune fraction. Matching dissociation times between limb blastemas and spleens, we demonstrate the effect of "over-digestion" in soft tissues. In the spleen, the Liberase enzyme cocktails produced the lowest yields, worst viability, and the greatest loss of immune cell surface markers, when compared with non-enzymatic and TrypLE dissociation. These examples provide a template for optimizing protocols for individual tissues while achieving the balance between cell recovery and the mitigation of cellular changes appropriate for downstream applications such as single-cell RNA sequencing and flow cytometry.

Conditional down-regulation of GreA impacts expression of rRNA and transcription factors, affecting Mycobacterium smegmatis survival

Gre, one of the conserved transcription factors in bacteria, modulates RNA polymerase (RNAP) activity to ensure processivity and fidelity of RNA synthesis. Gre factors regulate transcription by inducing the intrinsic-endonucleolytic activity of RNAP, allowing the enzyme to resume transcription from the paused and arrested sites. While Escherichia coli and a number of eubacteria harbor GreA and GreB, genus mycobacteria has a single Gre (GreA). To address the importance of the GreA in growth, physiology and gene expression of Mycobacterium smegmatis, we have constructed a conditional knock-down strain of GreA. The GreA depleted strain exhibited slow growth, drastic changes in cell surface phenotype, cell death, and increased susceptibility to front-line anti-tubercular drugs. Transcripts and 2D-gel electrophoresis (2D-PAGE) analysis of the GreA conditional knock-down strain showed altered expression of the genes involved in transcription regulation. Among the genes analysed, expression of RNAP subunits (β, β’ and ω), carD, hupB, lsr2, and nusA were affected to a large extent. Severe reduction in the expression of genes of rRNA operon in the knock-down strain reveal a role for GreA in regulating the core components of the translation process.

IMPS-06LOW DOSE RADIATION INDUCED IMMUNOMODULATION OF PEDIATRIC MEDULLOBLASTOMA

Medulloblastoma (MB) is the most common malignant brain tumor in children, and has been historically classified based on clinical markers (patient age, presence of metastases at diagnosis, extent of resection) and histopathological characteristics (classic, desmoplastic/nodular, and large cell/anaplastic). However, the recent gene expression profiling of a large number of tumors across multiple studies has provided evidence of four distinct medulloblastoma molecular subgroups (Wnt, Shh, Group 3, and Group 4), associated with remarkably different prognoses. While current therapies for medulloblastoma are often toxic, and not always effective, immunotherapy, designed to target these subgroups, may offer therapeutic improvement. Although monoclonal antibody (mAb) therapy has not yet been shown to be effective for the treatment of brain tumors, recent data indicate that radiation therapy can induce immunogenic modulation characterized by cell-surface phenotypic changes leading to augmented tumour cell/cytotoxic T-cell interaction. We examined the ability of radiation to upregulate mAb therapy targets. Our data showed that low dose radiation significantly increased cell-surface and total protein expression of mAb targets CD137 (a member of the TNF receptor superfamily), FGF, CD20, HER2, Major Histocompatability Complex (MHC) class I and intercellular adhesion molecule-1 (ICAM-I) in 3 out of 3 medulloblastoma cell lines. These findings highlight a mechanism for combining radiation with immunotherapy, to potentially expand the effect of targeted therapy in brain tumor treatment.

A genome wide transcriptional model of the complex response to pre-TCR signalling during thymocyte differentiation.

Developing thymocytes require pre-TCR signalling to differentiate from CD4-CD8- double negative to CD4+CD8+ double positive cell. Here we followed the transcriptional response to pre-TCR signalling in a synchronised population of differentiating double negative thymocytes. This time series analysis revealed a complex transcriptional response, in which thousands of genes were up and down-regulated before changes in cell surface phenotype were detected. Genome-wide measurement of RNA degradation of individual genes showed great heterogeneity in the rate of degradation between different genes. We therefore used time course expression and degradation data and a genome wide transcriptional modelling (GWTM) strategy to model the transcriptional response of genes up-regulated on pre-TCR signal transduction. This analysis revealed five major temporally distinct transcriptional activities that up regulate transcription through time, whereas down-regulation of expression occurred in three waves. Our model thus placed known regulators in a temporal perspective, and in addition identified novel candidate regulators of thymocyte differentiation.

Desensitization induces hyporesponsiveness and cell-surface phenotype changes on wild-type and humanized mouse mast cells

Background Rapid drug desensitization (DST) protocols have been developed based on clinical evidence, but in vitro studies are lacking. Understanding the mechanisms involved in the early stages of DST will allow improvements in patients’ treatment. The aim of this study is to demonstrate and characterize the induction of hyporesponsiveness in murine mast cells by desensitization. Methods We assessed the effect of rapid desensitization on murine bone marrow derived mast cells (BMMC). Experiments with three diferent types of murine BMMC were done: wild-type, LILRB4-/-, and transgenic expressing the human receptor FceRI. Wild-type and LILRB4-/- BMMC were sensitized with anti-DNP IgE and stimulated with DNP, while transgenic BMMC were sensitized with concentrated human serum of allergic subjects and stimulated with the respective allergen. BMMC were stimulated through desensitization or single activation, with optimal or suboptimal doses of antigen. Comparisions were made according to the percentage of b-Hexosaminidase (b-Hex) release by BMMC and the expression of LAMP-1 on the surface of these cells. Furthermore, expression of FceRI, PDL1 and LILRB4 on the surface of BMMC were also assessed. Results

Expanding the use of monoclonal antibody therapy of cancer by using ionising radiation to upregulate antibody targets

Background:Monoclonal antibody (mAb) therapy for the treatment of solid and haematologic malignancies has shown poor response rates as a monotherapy. Furthermore, its use is limited to tumours expressing certain molecular targets. It has been shown that single-dose radiation can induce immunogenic modulation that is characterised by cell-surface phenotypic changes leading to augmented tumour cell/cytotoxic T-cell interaction.Methods:We examined radiation's ability to upregulate mAb therapy targets. We also used radiation to sensitise tumour cells to antibody-dependent cell-mediated cytotoxicity (ADCC).Results:Radiation significantly increased cell-surface and total protein expression of mAb targets HER2, EGFR, and CD20. Focusing on HER2, targeted by trastuzumab, we observed significant upregulation of HER2 following radiation of 3 out of 3 breast cancer cell lines, one of which was triple negative, as well as in residential stem-cell populations. HER2 upregulation was sustained up to 96 h following radiation exposure and was largely dependent on intracellular reactive oxygen species. Improved ADCC and sensitisation to the antiproliferative effects of trastuzumab demonstrated the functional significance of radiation-induced HER2 upregulation.Conclusions:We show that single-dose radiation enhances mAb therapy. These findings highlight a mechanism for combining radiation with immunotherapy and expand the patient population that can be treated with targeted therapy.

CXCR4 and vascular cell adhesion molecule 1 are key chemokine/adhesion receptors in the migration of cytokine‐activated T cells

To examine the migratory properties of cytokine-activated T (Tck) cells. Tck cells were generated by culture of peripheral blood T cells in the presence of interleukin-6 (IL-6), tumor necrosis factor α, and IL-2. Changes in cell surface phenotype were analyzed by flow cytometry. Chemotactic responsiveness was measured using in vitro chemotaxis assays and transendothelial migration through human umbilical vein endothelial cell monolayers. Levels of vascular cell adhesion molecule 1 (VCAM-1) were measured by sandwich enzyme-linked immunosorbent assay. Cytokine stimulation up-regulated the expression of chemokine receptors and integrins on Tck cells, including CXCR4, very late activation antigen 4 (VLA-4), and lymphocyte function-associated antigen 1. Increased expression of CXCR4 and VLA-4 integrin resulted in concentration-dependent chemotaxis to their ligands, stromal cell-derived factor 1 (SDF-1) and VCAM-1, which could be selectively blocked using a specific CXCR4 inhibitor and antibodies against VLA-4. Increased expression of VLA-4 also resulted in increased transendothelial migration of Tck cells, which could be abrogated using blocking antibodies against VLA-4. Tck cells also showed an increased chemotactic response to rheumatoid arthritis (RA) fibroblast-like synoviocytes cultured in vitro, which could be blocked using inhibitors against VLA-4 and CXCR4. The activated phenotype of Tck cells results in increased migratory responsiveness to SDF-1 and soluble VCAM-1, which are among the chemokines and proteins found elevated in the RA synovial joint environment. Cytokine-dependent activation may contribute to RA pathogenicity by promoting T cell recruitment to and retention in the joint, perpetuating the inflammatory cascade in RA.

Infection of Dendritic Cells by a γ2-Herpesvirus Induces Functional Modulation

The murine gamma-herpesvirus-68 (gammaHV68) establishes viral latency in dendritic cells (DCs). In the present study, we examined the specific consequences of DC infection by gammaHV68, both in vivo and in vitro. Ex vivo analysis of infected mice showed that the virus colonizes respiratory DCs very early after infection and that all subsets of splenic DCs analyzed are viral targets. We have developed and characterized an in vitro model of gammaHV68 infection of DCs. Using this model, we demonstrated that viral infection neither induces full DC maturation nor interferes with exogenous activation, which is assessed by cell surface phenotypic changes. However, whereas gammaHV68 infection alone failed to elicit cytokine secretion, IL-10 secretion of exogenously activated DCs was enhanced. Furthermore, gammaHV68-infected DCs efficiently stimulated virus-specific T cell hybridomas but failed to induce alloreactive stimulation of normal T cells. These data indicate that viral infection doesn't interfere with Ag processing and presentation but does interfere with the ability of DCs to activate T cells. The inhibition of T cell activation was partially reversed by blocking IL-10. Analysis of infected mice shows elevated levels of IL-10 expression in DCs and that lack of endogenous IL-10 is associated with decreased gammaHV68 long-term latency. Taken together, these observations indicate that gamma2-herpesvirus infection of DCs is a mechanism of viral immune evasion, partially mediated by IL-10.

Severe Acute Respiratory Syndrome and the Innate Immune Responses: Modulation of Effector Cell Function without Productive Infection

Severe acute respiratory syndrome (SARS) caused by a novel human coronavirus (CoV), designated SARS-CoV, is a highly contagious respiratory disease with the lungs as a major target. Although the exact mechanism of SARS-CoV pathogenesis remains unknown, an intense, ill-regulated local inflammatory response has been suggested as partially responsible for the devastating lung pathology. We investigated the interaction of SARS-CoV with human macrophages (Mphi) and dendritic cells (DC), two key innate immune cells of the host immune system, by focusing on their susceptibility to viral infection and subsequent responses (e.g., phenotypic maturation, T cell-priming activity, phagocytosis, and cytokine production). We found neither cell to be permissive for SARS-CoV replication. However, incubation of Mphi and DC with live, but not gamma irradiation-inactivated, viruses appeared to better sustain their viability. Also, exposure to infectious SARS-CoV led to the phenotypic and functional maturation of DC, with regard to MHC class II and costimulatory molecule expression, T cell-stimulatory capacity, and cytokine production, respectively. Cytokine production was also observed for Mphi, which were refractory to cell surface phenotypic changes. Strikingly, live SARS-CoV could further prime cell types to respond to a suboptimal dose of bacterial LPS (100 ng/ml), resulting in massive release of IL-6 and IL-12. However, the endocytic capacity (e.g., Ag capture) of Mphi was significantly compromised upon exposure to infectious SARS-CoV. This study is the first demonstration that although SARS-CoV does not productively infect human Mphi or DC, it appears to exert differential effects on Mphi and DC maturation and functions, which might contribute to SARS pathogenesis.

Function of Bruton's tyrosine kinase during B cell development is partially independent of its catalytic activity.

The Tec family member Bruton's tyrosine kinase (Btk) is a cytoplasmic protein tyrosine kinase that transduces signals from the pre-B and B cell receptor (BCR). Btk is involved in pre-B cell maturation by regulating IL-7 responsiveness, cell surface phenotype changes, and the activation of lambda L chain gene rearrangements. In mature B cells, Btk is essential for BCR-mediated proliferation and survival. Upon BCR stimulation, Btk is transphosphorylated at position Y551, which promotes its catalytic activity and subsequently results in autophosphorylation at position Y223 in the Src homology 3 domain. To address the significance of Y223 autophosphorylation and the requirement of enzymatic activity for Btk function in vivo, we generated transgenic mice that express the autophosphorylation site mutant Y223F and the kinase-inactive mutant K430R, respectively. We found that Y223 autophosphorylation was not required for the regulation of IL-7 responsiveness and cell surface phenotype changes in differentiating pre-B cells, or for peripheral B cell differentiation. However, expression of the Y223F-Btk transgene could not fully rescue the reduction of lambda L chain usage in Btk-deficient mice. In contrast, transgenic expression of kinase-inactive K430R-Btk completely reconstituted lambda usage in Btk-deficient mice, but the defective modulation of pre-B cell surface markers, peripheral B cell survival, and BCR-mediated NF-kappaB induction were partially corrected. From these findings, we conclude that: 1) autophosphorylation at position Y223 is not essential for Btk function in vivo, except for regulation of lambda L chain usage, and 2) during B cell development, Btk partially acts as an adapter molecule, independent of its catalytic activity.

Effect of inhaled endotoxin on airway and circulating inflammatory cell phagocytosis and CD11b expression in atopic asthmatic subjects

Background: In a cohort of 8 normal and 10 allergic asthmatic volunteers, we previously reported that inhalation of 5 μg of endotoxin (LPS) induced airway inflammation that correlated with CD14 expression that was, in turn, correlated with eosinophil numbers in the airway. Macrophage and neutrophil functions have been reported to be modified by endotoxin in vitro and in vivo, and response to endotoxin is mediated largely by airway phagocytes and related to allergic inflammation. Objective: We sought to examine functional and cell-surface phenotype changes in phagocytes recovered from atopic asthmatic subjects after endotoxin challenge. Methods: Sputum and peripheral blood from 10 allergic asthmatic subjects was recovered after saline and LPS challenge. Assessment of phagocytosis and cell-surface phenotype (CD11b, CD14, and CD64) was performed on phagocytes obtained from sputum (n = 7) and blood samples (n = 10). Results: Phagocytosis of blood and sputum phagocytes was blunted after LPS challenge in a fashion that correlated with the increase in airway neutrophils after LPS challenge. Cell-surface expression of CD14 (membrane-bound CD14) was increased in sputum cells, whereas CD11b was decreased in sputum and circulating phagocytes. Baseline expression of CD11b in blood correlated with the magnitude of the neutrophil response after LPS inhalation, as well as (inversely) with baseline airway eosinophil levels. Conclusions: Inhalation of endotoxin at levels adequate to induce a neutrophil influx to the airways (but not systemic symptoms) results in decreased phagocytosis in both airway and circulating cells and modifies CD11b expression in a way that implicates its involvement in phagocyte responsiveness to inhaled LPS. (J Allergy Clin Immunol 2003;112:353-61.)

Impaired precursor B cell differentiation in Bruton's tyrosine kinase-deficient mice.

Bruton's tyrosine kinase (Btk) is a cytoplasmic signaling molecule that is crucial for precursor (pre-B) cell differentiation in humans. In this study, we show that during the transition of large cycling to small resting pre-B cells in the mouse, Btk-deficient cells failed to efficiently modulate the expression of CD43, surrogate L chain, CD2, and CD25. In an analysis of the kinetics of pre-B cell differentiation in vivo, Btk-deficient cells manifested a specific developmental delay within the small pre-B cell compartment of about 3 h, when compared with wild-type cells. Likewise, in in vitro bone marrow cultures, Btk-deficient large cycling pre-B cells showed increased IL-7 mediated expansion and reduced developmental progression into noncycling CD2(+)CD25(+) surrogate L chain-negative small pre-B cells and subsequently into Ig-positive B cells. Furthermore, the absence of Btk resulted in increased proliferative responses to IL-7 in recombination-activating gene-1-deficient pro-B cells. These findings identify a novel role for Btk in the regulation of the differentiation stage-specific modulation of IL-7 responsiveness in pro-B and pre-B cells. Moreover, our results show that Btk is critical for an efficient transit through the small pre-B cell compartment, thereby regulating cell surface phenotype changes during the developmental progression of cytoplasmic mu H chain expressing pre-B cells into immature IgM(+) B cells.

Flow cytometric measurement of intracellular cytokines

The identification of distinct T helper lymphocyte subsets (Th1/2) with polarised cytokine production has opened up new fields in immunobiology. Of the several alternative methods of monitoring cytokine production, flow cytometric analysis of intracellular staining has distinct advantages and pitfalls. It allows high throughput of samples and multiparameter characterisation of cytokine production on a single cell basis without the need for prolonged in vitro culture and cloning. However, these methods may cause important changes in cell surface phenotype which can make interpretation difficult.

The effect of total lymphoid irradiation and low-dose steroids on T lymphocyte populations in multiple sclerosis: correlation with clinical and MRI status

We have monitored the cell surface phenotypic changes occurring in T, B and NK cells of chronic progressive multiple sclerosis (MS) patients after total lymphoid irradiation (TLI) plus low-dose prednisone (TLI-LDP) therapy in comparison to sham TLI-LDP. TLI-LDP resulted in a marked reduction in the relative and absolute number of total CD3 + T cells, CD4 + helper T cells, CD4 +CD45RA + naive T cells and CD19 + B cells for at least 1 year after treatment. No change occurred in the percent CD8 + T cells although the number of these cells declined after radiotherapy. The CD4/CD8 T cell ratio was also decreased. The relative percent of CD16 + NK cells increased steadily after TLI-LDP while the number of NK cells transiently declined but returned to baseline values 1 year later. An increase in the percent of CD2 +CD3 − cells and a decrease in their number after therapy was also observed. In contrast, no significant changes in the number of T, B or NK cells were seen in the MS patients receiving sham TLI-LDP. These results provide further evidence that radiotherapy causes a reduction of immunocompetent T and B cells and that a population of possibly NK cells and/or immature T cells appears to be repopulating the circulation after TLI. In addition, a correlation was observed between alterations in lymphocyte populations and the presence or absence of contrast enhancing or new T 2 lesions on brain magnetic resonance imaging (MRI) in the TLI-LDP treated MS patients. Patients devoid of contrast enhancing or new T 2 lesions had a decreased percentage of CD3 + and CD4 + T cells prior to therapy and at six months following TLI-LDP compared to patients with such lesions. An association was also observed between stability in disease activity as determined on the Expanded Disability Status Scale and relative values of CD3 + T cells.

Distinct phenotypes of antigen-selected CD8 T cells emerge at different stages of an in vivo immune response.

We have previously described a unique system for identifying Ag-selected CD8 T cells during an in vivo response in normal mice. In this system, lymphocytes isolated from DBA/2 mice injected i.p. with HLA-CW3 transfected syngeneic (H-2d) P815 cells show a remarkable expansion of CD8 cells that utilize TCR expressing the V beta 10 gene segment and additional structural features characteristic of Kd-restricted CW3-specific CTL clones. We have now taken advantage of this system to characterize the surface phenotype of CD8 cells selected by Ag in vivo. We observed several distinct phenotypes at different stages of the response. At the peak of the response, Ag-selected cells were low in CD62L and CD45RB expression but displayed high levels of CD44. In addition, there was a partial down-regulation of CD8 and TCR. Cells of this phenotype were present in lymphoid tissues for several mo after immunization. Much later in the response, Ag-selected cells expressed higher levels of CD8 and TCR. Moreover, a distinct subset of these long-term immune cells emerged that now expressed CD62L and CD45RB. Analysis of CD8 cells from different tissues also revealed certain differences, particularly in TCR and co-receptor levels from liver-derived cells compared with circulating cells at the peak of the response. Our findings suggest that the function of Ag-selected CD8 cells may be regulated over time and according to location by subtle changes in cell-surface phenotype.

Cell surface phenotypic changes induced in H9 T cells chronically infected with HTLV type I or HIV type 1 or coinfected with the two viruses.

To investigate whether HTLV-I infection, HIV-I infection, or HIV-I infection of HTLV-I-infected cells affect the expression of cellular surface molecules, an HTLV-I-infected T cell line derived from the H9 T cell line was established (H36). H9 cells uninfected or infected with HTLV-I were then infected with HIV-1. We have compared the density of different surface markers on these three infected H9 T cell lines. These markers consist of T cell-specific antigens (CD2, CD3, CD4, and CD8), activated T cell antigens (CD25 and CD71), major histocompatibility complex (MHC) antigens (class I and II), and adhesion molecules (LFA-1 and ICAM-1). The experiments reported in this article show that chronic HTLV-I infection, HIV-1 infection, and HIV-1 infection of HTLV-I-infected T cells modulate the expression of several immunologically important cell surface antigens. The nature and the extent of T lymphoid cell phenotypic modulation depend on the infecting virus. Furthermore, HTLV-I and HIV-1 interact with each other in the phenotypic modulation of coinfected cells.

In Vitro Expansion of Tumor-Specific, HLA-Restricted Human CD8+ Cytolytic T Lymphocytes

The effect of cytokines with human recombinant interleukin-2 (rIL-2) on cytolytic T cell (CTL) generation was studied. Lymphocytes were isolated from involved lymph nodes of melanoma patients and expanded in medium containing rIL-2 alone or in combination with other human cytokines (rIL-1, rIL-4, rIL-6, and recombinant human tumor necrosis factor-α (rTNFα)). Lymphocytes incubated with rIL-2 alone did not grow, whereas addition of the other cytokines augmented IL-2-mediated lymphocyte proliferation. In all cultures, the majority of expanded lymphocytes were CD3+, CD56- T cells. Lymphocytes cultured with rIL-1, rIL-2, rIL-4, and rIL-6 exhibited cytolytic activity specific for autologous melanoma, which increased during the culture period (24.08 and 58.18% at 16 and 30 days in culture, respectively) without detectable changes in cell surface phenotype and remained high even after 100 days in culture. Moreover, the cytolytic activity was inhibited by monoclonal antibodies (mAbs) against HLA-class I, CD3, and CD8 molecules but not by mAbs against HLA-class II or CD4 molecules. Lymphokine-activated killer (LAK) activity was detected in lymphocytes cultured with rIL-1, rIL-2, and rIL-6 in the presence or absence of rTNFα. These data indicate that lymphocytes derived from melanoma-invaded lymph nodes and cultured in the presence of rIL-1, rIL-2, rIL-4, and rIL-6 offers an efficient system to expand CD8+ CTLs with HLA-restricted cytolytic specificity against autologous tumor cells.

An Activated CD8 + T Cell Phenotype Correlates with Anti-HIV Activity and Asymptomatic Clinical Status

We have examined the relation of cell surface marker phenotype to the anti-human immunodeficiency virus (HIV) function of CD8 + cells from individuals at various clinical stages of HIV infection. Multiparametric flow cytometry analysis demonstrated that the most significant changes in cell surface phenotype was found within the CD8 + cell subset expressing HLA-DR and CD28. These changes in the levels of CD28 and HLA-DR expression on CD8 + cells were found to be related to antiviral activity and have clinical relevance based on three pieces of evidence: (1) strong CD8 + cell antiviral responses were associated in infected individuals with high levels of HLA-DR + and CD28 + subsets; (2) CD8 + cell anti-HIV activity in vitro resides predominantly in the separated CD8 + cell subsets that express HLA-DR or CD28; and (3) in longitudinal studies, CD8 + cell anti-HIV activity decreased as an individual progressed from a healthy state to an AIDS condition. Taken together, the data suggest that the CD8 + cell subset identified phenotypically as a CD8 + CD28 + HLA-DR + cell is responsible for natural anti-HIV activity. Longitudinal studies should determine if alterations in this subset can be used as a prognostic indicator for disease progression.

Characterization of a novel cell-surface molecule expressed on subpopulations of activated T and B cells.

A mAb, GL7, is described that reacts with a 35-kDa protein on subsets of activated mouse B cells as well as activated CD4+ and CD8+ peripheral T cells. In normal mice analyzed by flow cytometry, GL7 bound at low surface density to 0 to 9% of splenic B cells and 0 to 1% of splenic T cells. In contrast, GL7 bound at high density to a subpopulation comprising approximately 20% of TCR-bright thymocytes, and to B220+ cells in the bone marrow. The activation of B cells by various stimuli resulted in high levels of expression of the surface molecule identified by GL7 on up to 70% of B cells after 48 h; the remaining B cells expressed low or undetectable levels of this molecule, despite evidence of other activation-specific changes in cell-surface phenotype. The GL7-positive population of B cells induced by IL-5 stimulation exhibited high levels of both proliferative and IgM secretory activity, whereas the GL7-negative population showed little of either activity. Activation of splenic T cells with Con A for 48 h resulted in the expression of this determinant at high density on both CD4+ and CD8+ cells. GL7 thus appears to identify a previously uncharacterized cell-surface molecule expressed selectively on subpopulations of activated B and T cells as well as on discrete subpopulations of T and B lineage cells in vivo.

13-Cis retinoic acid enhances in vivo B-lymphocyte differentiation in patients with common variable immunodeficiency

Retinoic acid (RA) has been demonstrated to drive both phenotypic and functional in vitro differentiation of B cell hybridomas from patients with common variable immunodeficiency (CVI) who manifest an “intrinsic” defect in terminal B cell differentiation (J Exp Med 1988;168: 55–71). Therefore, we conducted an open trial to determine the effects of oral 13-cis RA (0.5 mg/kg/day; 12 weeks receiving and 12 weeks without drug) on in vivo B cell differentiation in subjects with CVI. At various times before, during, and after drug administration, patients' B cells were tested for changes in cell-surface phenotype and in vitro immunoglobulin production in response to recombinant cytokines. Before 13-cis RA, all patients had decreased Leu-8 coexpression on CD20 + cells. Seven of eight subjects demonstrated “normalization” of this phenotype after 8 to 16 weeks of 13-cis RA administration. Patients whose B cells demonstrated more than normal CD20 display also had a fall toward normal in this parameter. These effects persisted for 6 to 12 weeks after drug was stopped. It appears that 13-cis RA drives B cells of patients with CVI to express a more differentiated cell-surface phenotype and may promote functional differentiation in some patients.