Spontaneous transgenesis of human B lymphocytes.

DNA can cross the cell membrane by natural means, but the functional relevance of this phenomenon has not been fully elucidated. Here, we analyzed spontaneous transgenesis of human B cells using plasmid DNA coding for a functional immunoglobulin (Ig) heavy chain gene under the control of a B-cell-specific promoter. Using polymerase chain reaction (PCR), reverse transcriptase-PCR, and flow cytometry in combination, spontaneous transgenesis was documented in Burkitt's lymphoma cell lines, Epstein-Barr virus-transformed cell lines, and peripheral blood B lymphocytes of the mature naïve phenotype (IgM(+)/IgD(+)/CD27(-)). By immunoelectron microscopy, the internalized DNA was seen in the lysosomes/late endosomes and in the cytosol proximal to the nucleus. Importantly, spontaneously transgenic B cells processed and presented to major histocompatibility complex (MHC)-restricted T lymphocytes a peptide expressed in the transgenic product. This is the first demonstration that primary B lymphocytes possess a program for the spontaneous internalization of DNA, which in turn imparts the cell with new immunological functions. As spontaneous transgenesis is obtained using a nonviral vector, does not require prior cell activation, and is not associated with chromosomal integration, the findings reported here open new possibilities for genetic manipulations of mature naïve B lymphocytes for therapy and vaccination.

Outbreak of group A streptococcus septicemia in children. Clinical, epidemiologic, and microbiological correlates.

OBJECTIVE: To determine the epidemiologic, clinical, and microbiological features of group A streptococcus septicemia in children. DESIGN: A descriptive series of 34 cases over an 11-year period from 1980 through 1990. SETTING: An academically affiliated tertiary-care pediatric hospital, the principal referral center for the state of Colorado and surrounding states. PARTICIPANTS: Thirty-four patients with positive blood cultures for group A streptococcus (33 medical records were available). MAIN OUTCOME MEASURES: Yearly incidence and clinical features of cases; microbiological features of isolated organisms. RESULTS: There was a significant increase (P = .01) in the incidence of group A streptococcus bacteremia over an 11-year period, with 14 (41%) of these cases occurring in 1989 and 1990. Patients had a rapidly progressing illness, usually without preceding pharyngitis. The prominent M and T types were 1 (4) and 12 (4). Eleven (73%) of the 15 strains produced pyrogenic exotoxin B that significantly correlated with production of proteinase. CONCLUSION: There appears to be an increase in group A streptococcus bacteremia in children that is associated with a strain phenotype that suggests a change in organism virulence.

Effects of a 4-week freshwater fish (trout) diet on platelet aggregation, platelet fatty acids, serum lipids, and coagulation factors.

Eight healthy subjects consumed a diet in which all animal products were replaced by 750 g/day of freshwater trout. Platelet eicosapentaenoic acid (EPA) as a percentage of total platelet fatty acids rose from a prediet level of 0.2 +/- 0.4% to 3.4 +/- 1.6% after 4 weeks on the diet. Platelet arachidonic acid remained unchanged. Platelets became more hyperaggregable to collagen (p less than .025) but became hypoaggregable to arachidonic acid (p less than .05). The Ivy bleeding time became prolonged rising from a mean of 148 seconds before the diet to 168 seconds at 2 weeks and 202 seconds at 4 weeks. Serum lipids, coagulation profiles, and blood pressure remained unchanged. The changes induced by this diet were much less marked than changes induced by marine fish diets and diets supplemented by marine fish oil extracts, despite the fact that an equivalent amount of EPA was consumed and incorporated into platelets. These findings suggest that other substances, in addition to n-3 unsaturated fatty acids, may be responsible for the antithrombotic properties of marine fish.