A novel mutation at a probable heme-binding ligand in neutrophil cytochrome b558 in atypical X-linked chronic granulomatous disease.

A membrane-bound cytochrome b558, a heterodimer consisting of gp91-phox and p22-phox, is a critical component of the superoxide (O2-)-generating reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in phagocytes. Chronic granulomatous disease (CGD) is characterized by recurrent bacterial infection caused by a defect of the oxidase. Both subunits are absent from phagocytes in typical X-linked recessive CGD patients who are primarily defective in gp91-phox. We report here an atypical case of X-linked CGD in which neutrophils showed a complete absence of O2--forming NADPH oxidase activity, but a small amount (about 10% of control) of both subunits was detected by immunoblot analysis. Spectrophotometric studies of the neutrophils with a recently developed sensitive method gave no evidence for the heme spectrum in the cytochrome b558, of this CGD. Reverse transcription/polymerase chain reaction and sequence analysis revealed a C to T transition replacing histidine at amino acid position 101 (His101) by tyrosine in gp91-phox. These results provide evidence that His101 of gp91-phox is the one of the heme-binding ligands of cytochrome b558.

Spectrophotometric determination of neutrophil cytochrome b558 of chronic granulomatous disease.

BACKGROUND: Chronic granulomatous disease (CGD) is an inherited disease characterized clinically by severe recurrent bacterial infections from infancy. This disease is a disorder of the formation of superoxide (O2-) by the neutrophil NADPH oxidase system, mostly due to defects in cytochrome b558 (cyt b558), which is one of the oxidase components. Diagnosis of CGD has been performed by the assay of the O2- forming activity, immunological determination of defects in the oxidase components, and or spectrophotometry of cyt b558. However, spectrophotometric analysis of the b-type heme is difficult with small amounts of blood from infant CGD patients, as the limited amounts of neutrophils are contaminated with a relatively high ratio of hemoglobin (Hb) that interferes with the heme spectrum of cyt b558. This report presents an accurate method for the spectrophotometric analysis of cyt b558 in a small amount of CGD neutrophils that were treated with CO gas in a safe procedure instead of the previously reported CO-bubbling method. METHODS AND RESULTS: The difference of the reduced minus oxidized cyt b558 spectrum was measured under no interference from oxy Hb at the alpha and beta bands and differentiated as d[delta A]/d lambda (lambda = wavelength) to obtain further evidence for the defects of the cyt b558 heme spectrum. The interference from CO-insensitive met Hb was eliminated by subtracting the absorption peak at the Soret (gamma) band of the contaminating met Hb, which was estimated from the CO-treated and untreated spectra of the same, hemolyzed sample. CONCLUSIONS: This spectrophotometric method is feasible for the determination of abnormality and heme content of cyt b558 with a small amount of CGD neutrophils in 10-20 mL of blood even in the presence of contaminating Hb.

Treatment of acute lymphoblastic leukemia in the Tokyo Children's Cancer Study Group--preliminary results of L84-11 protocol.

The Tokyo Children's Cancer Study Group (TCCSG) has performed prospective randomized controlled studies since 1984 for childhood acute lymphoblastic leukemia (ALL). Four hundred and ninety-eight newly diagnosed patients were treated with 5 different regimens designated as S1, S2 for a standard risk group (SRG), H1 and H2 for a high risk group (HRG) and HEX for an extremely high risk group of patients. We added intermediate-dose methotrexate as early intensification therapy in the S2 and H2 groups to reduce extramedullary and medullary relapses. Event-free survival of all patients at 4 years 6 months from the start of this regimen (median follow-up period 32 months) was 67.5%. The CNS relapse rate was significantly decreased to 2.2% compared to previously reported studies and our own experience. There were some unexpected complications of the CNS such as myelopathy and/or leukoencephalopathy. For the SRG early ID-MTX seemed to be useful to improve the prognosis, but triple intrathecal injections (TIT) should be limited in number. The 24Gy cranial irradiation (CRX) was effective but possibly excessive for the HRG. As evidenced by the success of the HEX group regimen, more intensive multi-drug consolidation in the early post-remission phase might be necessary to improve further the prognosis and to make it possible to shorten the treatment periods.

Effects of prophylactic irradiation of acute lymphoblastic leukemia in the central nervous system of children.

The development of prophylactic therapy for acute lymphoblastic leukemia (ALL) in the central nervous system in children has resulted in an improvement of the prognosis and prolongation of patients' lives. On the other hand, late irradiation effects have increased with the improvement of the prognosis. Therefore, there is now an important need to lessen these late effects without deteriorating the prognosis. We have investigated the recurrence rate, the survival rate and the cause of death of ALL patients who were divided into a none prophylactic irradiation group and 15 Gy, 20 Gy and 24 Gy irradiation groups. The results show that the effect of prophylactic irradiation has been more effective in the 20 Gy group than that of the 24 Gy group. Furthermore, brain atrophy and leukoencephalopathy, which were investigated by X-ray CT in long-term survivors of post-prophylactic irradiation without recurrence, have been less in the 20 Gy group than in that of the 24 Gy group. This report presents the result that the most favorable dose for prophylactic irradiation for central nervous system leukemia of ALL in children is 20 Gy by a step-up method.