Impact of early intervention on comprehensive language and academic achievement in Japanese hearing-impaired children with cochlear implants.

OBJECTIVES: Early hearing detection and intervention (EHDI) is critical for achievement of age-appropriate speech perception and language development in hearing-impaired children. It has been 15 years since newborn hearing screening (NHS) was introduced in Japan, and its effectiveness for language development in hearing-impaired children has been extensively studied. Moreover, after over 20 years of cochlear implantation in Japan, many of the prelingual cochlear implant (CI) users have reached school age, and the effect of CI on language development have also been assessed. To identify prognostic factors for language development, audiological/language test scores and demographic factors were compared among prelingual severe-to-profound hearing-impaired children with CI divided into subgroups according to age at first hearing aid (HA) use and whether they received NHS. METHODS: Prelingual severe-to-profound deafened children from the Research on Sensory and Communicative Disorders (RSCD) project who met the inclusion criteria were divided into groups according to the age (in months) of HA commencement (before 6 months: group A, after 7 months: group B), and the presence or absence of NHS (groups C and D). Language development and socio-economic data were obtained from audiological/language tests and a questionnaire completed by caregivers, respectively. RESULTS: In total, 210 children from the RSCD project participated in this study. Group A (n=49) showed significantly higher scores on comprehensive vocabulary and academic achievement (p<0.05) than group B (n=161), with no difference in demographics except for significantly older age in group B. No differences in language scores were observed between group C (n=71) and group D (n=129), although participants of group D was significantly older and had used CIs longer (p<0.05). CONCLUSIONS: Early use of HAs until the CI operation may result in better language perception and academic achievement among CI users with prelingual deafness. A long-term follow-up is required to assess the usefulness of NHS for language development.

Effects of insulin-like growth factor-1 on B-cell precursor acute lymphoblastic leukemia.

Insulin-like growth factor-1 (IGF-1) is known to be a major growth factor with effects on various cell types, including hematopoietic cells, as well as neoplasms, and is regulated by IGF-binding proteins (IGFBPs). In this study, we investigated the effects of IGF-1 on B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cells. When the expression of IGF-1R in clinical samples of BCP-ALL was examined, five of thirty-two cases showed IGF-1R expression, whereas IGF-1R was expressed in most BCP-ALL cell lines. We observed that IGF-1 enhanced the proliferation of BCP-ALL cell lines that can be partially inhibited by IGFBP-1, -3, and -4, but not other IGFBPs. IGF-1 also partially inhibited dexamethasone-induced apoptosis, but not apoptosis mediated by VP-16 and irradiation. Interestingly, the proliferative effect of IGF-1 was partially blocked by inhibitors of MAPK and AKT, whereas the inhibition of dexamethasone-induced apoptosis was completely blocked by both inhibitors. Our data indicate that IGF-1 is involved in cell proliferation and apoptosis regulation in BCP-ALL cells. Since some BCP-ALL cases express IGF-1R, it appears to be a plausible target for prognostic evaluation and may represent a new therapeutic strategy.

Assessment package for language development in Japanese hearing-impaired children (ALADJIN) as a test battery for the development of practical communication.

OBJECTIVES: The measurement of language development in hearing-impaired children is an important step in assessing the appropriateness of an intervention. We proposed a set of language tests (the Assessment Package for Language Development in Japanese Hearing-Impaired Children [ALADJIN]) to evaluate the development of practical communication skills. This package consisted of communication skills (TQAID), comprehensive (PVT-R and SCTAW) and productive vocabulary (WFT), comprehensive and productive syntax (STA), and the STRAW. METHODS: A total of 638 children with greater than 70-dB hearing impairment were subjected to this set of language tests. Additional tests, including the PARS, the RCPM, and parental questionnaires, were administered to assess the backgrounds of the children. RESULTS: A trimodal distribution was observed among hearing-impaired children by the histogram-based analysis of each test. CONCLUSIONS: The ALADJIN is a useful Japanese-language evaluation kit for hearing-impaired children.

Language ability in the intermediate-scoring group of hearing-impaired children.

OBJECTIVES: Language development is a key issue in hearing-impaired children. However, interpersonal differences complicate our understanding of the situation. The bimodal or trimodal distribution of language scores in our other reports in this publication imply the presence of fundamental differences among these groups. The characteristic aspects of each group were profiled according to language data. METHODS: We divided 268 children with prelingual severe to profound hearing impairment into 3 groups according to their trimodal distribution observed on histogram-based analysis of their responses to the Test of Question-Answer Interaction Development. Test results in several language domains, including productive and comprehensive vocabulary, productive and comprehensive syntax, and academic achievement, were profiled and compared among these 3 groups. RESULTS: Significant differences were observed in the results of the Word Fluency Test, the Picture Vocabulary Test-Revised, and the Syntax Test of Aphasia among the 3 groups. No significant difference was observed between groups who were lower-scoring and intermediate-scoring on the academic achievement tests referred to as Criterion Referenced Test-II and the Standardized Comprehension Test for Abstract Words. Only the higher-scoring group showed excellent results. The demographic factors were not significantly different among the 3 groups. CONCLUSIONS: Relatively poor academic achievement despite fair language production was the dominant feature of the intermediate-scoring group. This profile might correlate with academic failure in school.

Language development, interpersonal communication, and academic achievement among Japanese children as assessed by the ALADJIN.

OBJECTIVES: Japanese-speaking children in a standard sample were subjected to a test battery (ALADJIN: Assessment Package for Language Development in Japanese Hearing-Impaired Children) to evaluate the effect of language development on both interpersonal communication skills and academic achievement. METHODS: A total of 414 preschool and school-age children without hearing impairment were included in this study. The following tests make up the ALADJIN: the Test of Question-Answer Interaction Development (TQAID), the Japanese Language by Criterion Referenced Test-II (CRT-II) for measuring academic achievement, the Picture Vocabulary Test-Revised (PVT-R), the Standardized Comprehension Test of Abstract Words (SCTAW), both parts of the Syntactic Processing Test for Aphasia (STA), and the Word Fluency Test (WFT). Means and standard deviations at each academic grade level were calculated, and a multiple regression analysis was performed. RESULTS: A ceiling effect was observed for the TQAID and the STA in children in grade 3 of elementary school, and the scores for the PVT-R, SCTAW, and WFT increased incrementally according to grade level. Multiple regression analysis revealed that the PVT-R, WFT, and STA (production) have predictive power for the results of the TQAID (R = 0.59; R2 = 0.58; p <0.0001), whereas the SCTAW and STA (comprehension) have predictive power for the results of the CRT-II. CONCLUSIONS: Both vocabulary and syntax are important in communication development among children. The results of our multiple regression analysis suggest that different language domains may play different roles in the development of interpersonal communication skills and in academic achievement. The development of interpersonal communication skills is largely based on productive vocabulary and syntax abilities, whereas academic achievement is largely based on comprehensive vocabulary and syntax abilities. Children who have difficulties in either area should be evaluated with detailed language assessment tools such as the ALADJIN in an effort to aid in the selection of appropriate intervention.

Syntactic development in Japanese hearing-impaired children.

OBJECTIVES: This study examined syntactic development of auditory comprehension of sentences in Japanese-speaking school-age children with and without hearing impairment. METHODS: In total, 592 preschool and school-age children (421 normal-hearing and 171 hearing-impaired) were included in this cross-sectional observation study conducted using the Syntactic Processing Test for Aphasia for Japanese language users. Linear regression analysis was used to determine the estimated age at which each syntactic structure was acquired. RESULTS: Acquisition of syntactic structures was observed in hearing-impaired and normal-hearing children. Basic word order sentences of agent-object-verb and the goal benefactive construction were acquired at preschool age (earlier group), whereas reverse word order sentences of object-agent-verb, source benefactive construction, passive voice, and relative clauses were acquired at school age (later group). The results showed that many hearing-impaired children may not acquire Japanese grammatical structures until the age of 12 years. CONCLUSIONS: Adequate screening for language development for school-age hearing-impaired children is required for an effective intervention.

Human osteoblasts support hematopoietic cell development in vitro.

BACKGROUND/AIM: Although osteoblasts are thought to be the major component of the hematopoietic stem cell niche in the bone marrow microenvironment, the role of osteoblasts in hematopoiesis is still unclear. The ability of human osteoblasts to support early hematopoiesis was investigated. METHODS AND RESULTS: Human CD34+ bone marrow cells cultured on human osteoblasts were capable of surviving without addition of cytokines and differentiated into myeloid cells with slight proliferation. The results of immunohistochemical experiments suggested activation of FAK and AKT in hematopoietic cells attached to osteoblasts. When stem cell factor, Flt3-L, and IL-3 were added to the coculture system, each cytokine distinctively enhanced proliferation and differentiation of CD34+ bone marrow cells. CONCLUSION: The results suggest that human osteoblasts have the ability to support hematopoietic cell development in vitro.

Inducible expression of chimeric EWS/ETS proteins confers Ewing's family tumor-like phenotypes to human mesenchymal progenitor cells.

Ewing's family tumor (EFT) is a rare pediatric tumor of unclear origin that occurs in bone and soft tissue. Specific chromosomal translocations found in EFT cause EWS to fuse to a subset of ets transcription factor genes (ETS), generating chimeric EWS/ETS proteins. These proteins are believed to play a crucial role in the onset and progression of EFT. However, the mechanisms responsible for the EWS/ETS-mediated onset remain unclear. Here we report the establishment of a tetracycline-controlled EWS/ETS-inducible system in human bone marrow-derived mesenchymal progenitor cells (MPCs). Ectopic expression of both EWS/FLI1 and EWS/ERG proteins resulted in a dramatic change of morphology, i.e., from a mesenchymal spindle shape to a small round-to-polygonal cell, one of the characteristics of EFT. EWS/ETS also induced immunophenotypic changes in MPCs, including the disappearance of the mesenchyme-positive markers CD10 and CD13 and the up-regulation of the EFT-positive markers CD54, CD99, CD117, and CD271. Furthermore, a prominent shift from the gene expression profile of MPCs to that of EFT was observed in the presence of EWS/ETS. Together with the observation that EWS/ETS enhances the ability of cells to invade Matrigel, these results suggest that EWS/ETS proteins contribute to alterations of cellular features and confer an EFT-like phenotype to human MPCs.

Interleukin-7 contributes to human pro-B-cell development in a mouse stromal cell-dependent culture system.

OBJECTIVE: The role of interleukin (IL)-7 in human B lymphopoiesis is still controversial. We used an in vitro culture system to verify involvement of IL-7 in development of human pro-B cells from hematopoietic stem cells. MATERIALS AND METHODS: Human CD34(+) bone marrow cells were cultured for 4 weeks on MS-5 mouse stromal cells to induce pro-B cells. Expression of IL-7 receptor alpha or other B-cell differentiation marker genes on cultured human CD34(+)bone marrow cells was investigated by reverse transcription polymerase chain reaction (RT-PCR). Colony assay of human CD34(+) bone marrow cells was also performed to determine the effect of IL-7 on colony-forming ability. Neutralizing antibody or reagent that eliminates the effect of IL-7 was added to the culture system, and the number of pro-B cells induced was estimated by flow cytometry. RESULTS: RT-PCR analysis revealed mRNA expression of IL-7 receptor alpha as well as B-cell differentiation marker genes in not only CD19(+) pro-B cells but also CD19(-) CD33(-) cells induced from CD34(+) bone marrow cells after cultivation for 4 weeks on MS-5 cells. Addition of anti-mouse IL-7 antibody, anti-human IL-7 receptor alpha antibody, or JAK3 kinase inhibitor reduced the number of pro-B cells induced, demonstrating that elimination of IL-7 reduces pro-B-cell development. Addition of anti-mouse IL-7 antibody emphasized the colony-forming ability of burst-forming unit erythroid cells. CONCLUSIONS: IL-7 produced by MS-5 cells is required for human pro-B-cell development from CD34(+)bone marrow cells in our culture system, and IL-7 appears to play a certain role in early human B lymphopoiesis.

Characterization of monocyte-macrophage-lineage cells induced from CD34+ bone marrow cells in vitro.

We characterized the expression of cell surface antigens and cytokine-secreting ability of monocyte-macrophage-lineage cells induced in vitro from CD34+ bone marrow cells. After cultivation for 3 weeks, we observed 2 distinct cell fractions: a floating small, round cell fraction and an adherent large, protruding cell fraction. Both cell fractions expressed myelocyte-monocyte-lineage antigens, but mature-macrophage markers such as CD206 were expressed only by the adherent cells. An assessment of cells cultured for 5 weeks revealed spontaneous secretion of interleukin 8 (IL-8) and IL-6, and lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-alpha) secretion in both fractions, but only the adherent cell fraction secreted IL-10 after LPS stimulation. In contrast, both fractions of cells cultured for 3 weeks spontaneously secreted low levels of IL-8, but none of the other cytokines. Upon LPS stimulation, the cells secreted IL-6 and TNF-alpha, but not IL-10. We also assessed the effect of granulocyte colony-stimulating factor (G-CSF) pretreatment on TNF-alpha secretion by each cell fraction and found that G-CSF reduced TNF-alpha secretion only in the adherent fraction of cells cultured for 3 weeks. Monocyte-macrophage-lineage cells induced in vitro should provide an ideal model for functional analysis of monocyte-macrophage cells.

Involvement of insulin-like growth factor-I and insulin-like growth factor binding proteins in pro-B-cell development.

OBJECTIVE: Insulin-like growth factor (IGF)-binding proteins (IGFBPs) are a family of proteins thought to modulate IGF function. By employing an in vitro culture system of human hematopoietic stem cells cocultured with murine bone marrow stromal cells, we examined the effects of IGF-I and IGFBPs on early B-cell development. MATERIALS AND METHODS: Human CD34(+) bone marrow cells were cocultured with murine stromal MS-5 cells for 4 weeks, and pro-B-cell number was analyzed by flow cytometry. After administration of reagents that are supposed to modulate IGF-I or IGFBP function to the culture, the effect on pro-B-cell development was examined. RESULTS: After cultivation for 4 weeks, effective induction of pro-B-cell proliferation was observed. Experiments using several distinct factors, all of which neutralize IGF-I function, revealed that impairment of IGF-I function results in a significant reduction in pro-B-cell development from CD34(+) cells. In addition, when the effect of recombinant proteins of IGFBPs and antibodies against IGFBPs were tested, IGFBP-3 was found to inhibit pro-B-cell development, while IGFBP-6 was required for pro-B-cell development. CONCLUSIONS: IGF-I is essential for development of bone marrow CD34(+) cells into pro-B cells. Moreover, IGFBPs are likely involved in regulation of pro-B-cell development.

Laminin binding protein, 34/67 laminin receptor, carries stage-specific embryonic antigen-4 epitope defined by monoclonal antibody Raft.2.

We previously produced monoclonal antibodies against the detergent-insoluble microdomain, i.e., the raft microdomain, of the human renal cancer cell line ACHN. Raft.2, one of these monoclonal antibodies, recognizes sialosyl globopentaosylceramide, which has the stage-specific embryonic antigen (SSEA)-4 epitope. Although the mouse embryonal carcinoma (EC) cell line F9 does not express SSEA-4, some F9 cells stained with Raft.2. Western analysis and matrix-assisted laser desorption ionization-time of flight mass spectrometry identified the Raft.2 binding molecule as laminin binding protein (LBP), i.e., 34/67 laminin receptor. Weak acid treatment or digestion with Clostridium perfringens sialidase reduced Raft.2 binding to LBP on nitrocellulose sheets and [(14)C]galactose was incorporated into LBP, indicating LBP to have a sialylated carbohydrate moiety. Subcellular localization analysis by sucrose density-gradient centrifugation and examination by confocal microscopy revealed LBP to be localized on the outer surface of the plasma membrane. An SSEA-4-positive human EC cell line, NCR-G3 cells, also expressed Raft.2-binding LBP.

Dietary bioflavonoids induce apoptosis in human leukemia cells.

Dietary bioflavonoids are secondary metabolites of plants that are known to have a variety of bio-effects, including anti-cancer activity. In this study, we examined the effects of flavonoids on the growth of human leukemia cells and found that certain flavonoids induce apoptosis in a variety of human leukemia cells. The apoptosis induced by bioflavonoids was dose-dependent and was accompanied by a disruption of the mitochondrial transmembrane potential and the activation of caspase. Our data suggests that dietary bioflavonoids may be useful chemotherapeutic reagents for leukemia patients.

Development of novel monoclonal antibody 4G8 against swine leukocyte antigen class I alpha chain.

A mouse monoclonal antibody (MAb) was generated against swine leukocyte antigen (SLA) class I alpha chain. A newly developed series of MAb clones that react with pan leukocytes were selected and tested by immuno-histochemistry using SLA class I alpha chain expressing Cos-7 cells. Among them, MAb 4G8 was characterized by the following features: (1) 4G8 reacted with Cos-7 cells transfected with SLA class I alpha chain from the d haplotype, (2) 4G8 recognized epitopes that were different from those of commercially available anti-SLA class I MAbs 74-11-10 and PT85A, and (3) 4G8 could be used to immunostain frozen sections of thymus, spleen, lymph node, kidney, and liver tissues with good results.

Shiga toxin binding to globotriaosyl ceramide induces intracellular signals that mediate cytoskeleton remodeling in human renal carcinoma-derived cells.

Shiga toxin is a bacterial toxin consisting of A and B subunits. Generally, the essential cytotoxicity of the toxin is thought to be mediated by the A subunit, which possesses RNA cleavage activity and thus induces protein synthesis inhibition. We previously reported, however, that the binding of the Shiga toxin 1-B subunit to globotriaosyl ceramide, a functional receptor for Shiga toxin, induces intracellular signals in a manner that is dependent on glycolipid-enriched membrane domains, or lipid rafts. Although the precise role of this signaling mechanism is not known, here we report that Shiga-toxin-mediated intracellular signals induce cytoskeleton remodeling in ACHN cells derived from renal tubular epithelial carcinoma. Using confocal laser scanning microscopy, we observed that Shiga toxin 1-B treatment induces morphological changes in ACHN cells in a time-dependent manner. In addition, the morphological changes were accompanied by the redistribution of a number of proteins, including actin, ezrin, CD44, vimentin, cytokeratin, paxillin, FAK, and alpha- and gamma-tubulins, all of which are involved in cytoskeletal organization. The transient phosphorylation of ezrin and paxillin was also observed during the course of protein redistribution. Experiments using inhibitors for a variety of kinases suggested the involvement of lipid rafts, Src family protein kinase, PI 3-kinase, and RHO-associated kinase in Shiga toxin 1-B-induced ezrin phosphorylation. Shiga toxin 1-B-induced cytoskeletal remodeling should provide an in vitro model that can be used to increase our understanding of the pathogenesis of Shiga-toxin-mediated cell injury and the role of lipid-raft-mediated cell signaling in cytoskeletal remodeling.

Deficiency of BLNK hampers PLC-gamma2 phosphorylation and Ca2+ influx induced by the pre-B-cell receptor in human pre-B cells.

B-cell linker protein (BLNK) is a component of the B-cell receptor (BCR) as well as of the pre-BCR signalling pathway, and BLNK(-/-) mice have a block in B lymphopoiesis at the pro-B/pre-B cell stage. A recent report described the complete loss or drastic reduction of BLNK expression in approximately 50% of human childhood pre-B acute lymphoblastic leukaemias (ALL), therefore we investigated BLNK expression in human pre-B ALL cell lines. One of the four cell lines tested, HPB-NULL cells, was found to lack BLNK expression, and we used these human pre-B ALL cell lines that express and do not express BLNK to investigate the intracellular signalling events following pre-BCR cross-linking. When pre-BCR was cross-linked with anti-micro heavy-chain antibodies, significant phosphorylation of intracellular molecules, including Syk, Shc, ERK MAP kinase, and AKT, and an activation of Ras were observed without regard to deficiency of BLNK expression, suggesting that BLNK is not required for pre-BCR-mediated activation of MAP kinase and phosphatidyl-inositol 3 (PI3) kinase signalling. By contrast, phospholipase C-gamma2 (PLC-gamma2) phosphorylation and an increase in intracellular Ca(2+) level mediated by pre-BCR cross-linking were observed only in the BLNK-expressing cells, indicating that BLNK is essential for PLC-gamma2-induced Ca(2+) influx. Human pre-B cell lines expressing and not expressing BLNK should provide an in vitro model for investigation of the role of BLNK in the pre-BCR-mediated signalling mechanism.

Characterization of a shiga-toxin 1-resistant stock of vero cells.

Shiga toxins (Stxs, also referred to as verotoxins) were first described as a novel cytotoxic activity against Vero cells. In this study, we report the characterization of an Stx1-resistant (R-) stock of Vero cells. (1) When the susceptibility of R-Vero cells to Stx1 cytotoxicity was compared to that of Stx1-sensitive (S-) Vero cells by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, cell viability after 48-hr exposure to 10 pg/ml of Stx1 was greater than 80% and less than 15%, respectively. (2) Although both a binding assay of fluorescence-labeled Stx1 and lipid analysis indicated considerable expression of Gb3Cer, a functional receptor for Stxs, in both Vero cells, anti-Gb3Cer monoclonal antibodies capable of binding to S-Vero cells failed to effectively label R-Vero cells, suggesting a conformational difference in the Gb3Cer expressed on R-Vero cells. (3) The lipid analysis also showed that the R-Vero cells contained significant amounts of Gb4Cer. In addition, introduction of exogenous Gb4Cer into S-Vero cells slightly inhibited Stx1 cytotoxicity, suggesting some correlation between glycosphingolipid composition and Stx1 resistance. (4) Both butyrate treatment and serum depression eliminated the Stx1 resistance of R-Vero cells. (5) The results of the analysis by confocal microscopy suggest a difference in intracellular transport of Stx1 between R-Vero and S-Vero cells. Further study of R-Vero cells may provide a model of Stx1 resistance via distinct intracellular transport of Stx1.

Diagnostic importance of CD179a/b as markers of precursor B-cell lymphoblastic lymphoma.

Surrogate light chains consisting of VpreB (CD179a) and lambda5 (CD179b) are expressed in precursor B cells lacking a complete form of immunoglobulin and are thought to act as substitutes for conventional light chains. Upon differentiation to immature and mature B cells, CD179a/b disappear and are replaced with conventional light chains. Thus, these molecules may be useful as essential markers of precursor B cells. To examine the expression of the surrogate light-chain components CD179a and CD179b in precursor B-cell lymphoblastic lymphoma, we analyzed tissue sections using immunohistochemistry techniques. Among a number of monoclonal antibodies for the surrogate light chains, VpreB8 and SL11 were found to detect CD179a and CD179b, respectively, in acetone-fixed fresh frozen sections. Moreover, we also observed VpreB8 staining in formalin-fixed, paraffin-embedded sections. Using these antibodies, we found that CD179a/b were specifically expressed in precursor B-cell lymphoblastic lymphomas, but not in mature B-cell lymphomas in childhood. Furthermore, other pediatric tumors that must be included in a differential diagnosis of precursor B-cell lymphoblastic lymphoma, including precursor T-cell lymphoblastic lymphoma, extramedullary myeloid tumors, and Ewing sarcoma, were also negative for both CD179a and CD179b. Our data indicate that CD179a and CD179b may be important markers for the immunophenotypic diagnosis of precursor B-cell lymphoblastic lymphomas.

Nephrotic syndrome associated with human parvovirus B19 infection.

A previously healthy 8-year-old Japanese boy developed nephrotic syndrome during the course of erythema infectiosum due to human parvovirus B19 (PVB19) infection. A renal biopsy showed mesangiocapillary proliferative glomerulonephritis with immune complex deposits associated with PVB19 virus. His renal involvement improved spontaneously.

Pre-B cell antigen receptor-mediated signal inhibits CD24-induced apoptosis in human pre-B cells.

We previously reported that the cross-linking of cluster of differentiation (CD)24 induces apoptosis in Burkitt's lymphoma cells and that this phenomenon can be enhanced by a B cell Ag receptor (BCR)-mediated signal. In this study, we extend our previous observation and report that CD24 also mediated apoptosis in human precursor-B acute lymphoblastic leukemia cell lines in the pro-B and pre-B stages accompanying activation of multiple caspases. Interestingly, simultaneous cross-linking of pre-BCR clearly inhibited CD24-mediated apoptosis in pre-B cells. We also observed that mitogen-activated protein kinases (MAPKs) were involved in the regulation of this apoptotic process. Pre-BCR cross-linking induced prompt and strong activation of extracellular signal-regulated kinase 1, whereas CD24 cross-linking induced the sustained activation of p38 MAPK, following weak extracellular signal-regulated kinase 1 activation. SC68376, a specific inhibitor of p38 MAPK, inhibited apoptosis induction by CD24 cross-linking, whereas anisomycin, an activator of p38 MAPK, enhanced the apoptosis. In addition, PD98059, a specific inhibitor of MEK-1, enhanced apoptosis induction by CD24 cross-linking and reduced the antiapoptotic effects of pre-BCR cross-linking. Collectively, whether pre-B cells survive or die may be determined by the magnitude of MAPK activation, which is regulated by cell surface molecules. Our findings should be important to understanding the role of CD24-mediated cell signaling in early B cell development.