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Notes: Summary Two mutants of Escherichia coli that are deficient in the penicillin-insensitive DD-endopeptidase have been isolated. The strain JE10874 (mepA) has about 10%–20% of the residual activity and another strain, JE10368 (mepB) has 40%–50% of the activity found in the wild-type, parental strain, PA3092. The penicillin-insensitive endopeptidase is a periplasmic enzyme. Genetic mapping studies show that the mutation mepA is located close to aroC (50 min) and the other mutation, mepB, is very close to malE (91 min) on the chromosome. These mutants grow normally under a wide range of growth conditions; other phenotypic properties of the mutants are very similar to those of the parent strain. A double mutant (mepA mepB), and a triple mutant (mepA mepB dacB), deficient in both penicillin-insensitive and penicillin-sensitive endopeptidases, were constructed. Again, these mutants grew normally. We conclude that either the very low level of residual enzyme activity in the mutants is enough for their survival or that the penicillin-insensitive endopeptidase is not essential for survival under laboratory conditions.

Notes: Abstract C3b receptor (CR1) expression by neutrophils (PMNs) and erythro-cytes (Es) from patients with chronic granulomatous disease (CGD) or with hyper-IgE, frequent infection (Job's) syndrome was compared with that of control subjects. The control subjects consisted of one group of patients with infections and a second group of normal, healthy individuals. Three quantitative assays were used: rosette formation with C3b-coated cellular intermediates (EAC43b), binding of radiolabeled monoclonal anti-CRl ([125I]anti-CRl) to PMN surfaces, and binding of the antibody to nonidet P-40 (NP-40) extracts of PMNs and Es in an immunoradiometric assay. Rosette formation by the PMNs of five male CGD patients was about 50% of that of paired normal control subjects, whereas the rosette formation of three female CGD patients was similar to that of the control subjects. Surface binding of [125I]anti-CRl to PMNs of 10 CGD patients was about half that of the normal subjects (mean percent binding was 2.33% for the CGD patients vs. 3.86% for the normal subjects, giving a difference of -1.53 ± 0.22%,P 〈 0,001 by the paired-samplet test). The degree of PMN binding was similarly low for both the male and the female CGD patients. Conversely, the binding of anti-CRl to the PMNs of 11 infected control patients appeared to be similar to that of the normal subjects (4.51% for the patient vs. 4.21% for the paired normal subjects). The infected control group originally included four Job's syndrome patients, and when this subgroup was analyzed separately, their PMNs were shown to bind significantly less anti-CRl than did the PMNs of the normal subjects (P 〈 0.01 by the paired-samplet test). In contrast, the other infected control patients showed higher-than-normal levels of anti-CR 1 binding (P 〈 0.05). When compared to that of the normal subjects, the total CR1 quantitated in PMN extracts was also lower than normal in CGD patients (P 〈 0.01 and in the PMN extracts of eight Job's syndrome patients tested (P 〈 0.01). The PMNs of the other infected control subjects were not significantly different from those of the normal subjects in total CRI expression. Extracts of Es from Job's syndrome patients also had fewer than normal CR1 (P 〈 0.02). On the other hand, CR1 levels in E extracts from the CGD patients and the other control patients were similar to those in the normal control subjects. Quantitations of C 3, C4, and factor B were normal in CGD. Significant levels of immune complexes were detected in serum samples from several CGD and Job's syndrome patients. However, the level of immune complexes did not correlate significantly with the CR1 deficit in CGD or Job's syndrome patients. Thus, in CGD patients, CRI expression of PMNs is below normal, while that of Es is normal; in Job's syndrome patients, both the PMN and the E CRI expression are below normal. These abnormalities do not appear to result from the frequent infections that occur in these diseases since the other infected control patients exhibit an above-normal amount of surface PMN CR1.