Follicular dendritic cells (FDC) in retroviral infection: host/pathogen perspectives

Summary: Follicular dendritic cells (FDC) are found in the follicles of virtually all secondary lymphoid tissues. In health, these cells trap and retain antigens (Ag) in the form of immune complexes and preserve them for months in their native conformation. FDC thus serve as a long-term repository of extracellular Ag important for induction and maintenance of memory responses. In retroviral infection. FDC trap and retain large numbers of retroviral particles with profound effects on FDC. FDC-trapped retrovirus induces follicular hyperplasia, and conventional Ag trapped prior to infection are lost and new Ag cannot be trapped. Concomitantly, antibody-forming cells (AFC) specific for Ag lost from FDC decrease follow I by loss of specific serum antibody (Ab). Eventually, FDC die and follicular lysis occurs. From the pathogen perspective, binding to FDC is remarkably beneficial, bringing together virus and activated target cells that are highly susceptible to infection. Furthermore, FDC permit HIV to infect surrounding cells even in the presence of a vast excess of neutralizing Ab. Preliminary data suggest that FDC maintain virus infectivity - even when the virus cannot replicate. Thus retrovirus infection monopolizes FDC networks, thereby transforming the FDC Ag repository into a highly infectious retroviral reservoir.     

Group A Streptococcal Antibodies in Subjects with or without Rheumatic Fever in Areas with High or Low Incidences of Rheumatic Fever

The levels of streptococcal antibody titers in populations with or without rheumatic fever from an area with a relatively high incidence of rheumatic fever and an area with a low incidence of this disease were compared. Streptococcal antibody titers were determined for two populations, each of which included children without rheumatic fever (nonrheumatic children) and rheumatic fever patients. The two populations were derived from two separate geographic areas, one with a high incidence of rheumatic fever (Grenada) and another with a low incidence of this disease (central Florida). The results revealed an absence of consistent differences in the geometric mean antibody titers between the nonrheumatic subjects and the rheumatic fever patients from Grenada. In the population from Grenada, the mean anti-streptolysin O and anti-DNase B titers were higher in the nonrheumatic controls (P of 0.085 and 0.029, respectively). However, the mean titer of the antibody to the group A streptococcal cell wall carbohydrate was higher in the rheumatic fever patients than in the nonrheumatic controls (P = 0.047). This finding contrasted with the finding that the means of all three streptococcal antibody titers in the patients with rheumatic fever were significantly higher than those in the nonrheumatic subjects from Florida (P = 0.01-<0.001). The reason for this paradoxical finding became evident when the streptococcal antibody titers of the nonrheumatic subjects from Grenada and Florida were compared, revealing significantly higher levels of all three antibodies in the nonrheumatic subjects from Grenada than in the nonrheumatic subjects from Florida (P < 0.001). These results suggest that nonrheumatic individuals in an area with a high incidence of rheumatic fever have inordinately elevated levels of streptococcal antibodies in serum. The presence of elevated streptococcal antibody titers in such a population, which probably reflects a high background prevalence of streptococcal infections, should be taken into consideration when evaluating the role of the group A streptococcus in nonpurulent complications of infections.     

Oculoauriculovertebral anomaly: Segregation analysis

Seventy-four families of probands with oculoauriculovertebral anomaly were evaluated, including 116 parents and 195 off-spring. Relatives were examined to identify ear malformations, mandibular anomalies, and other craniofacial abnormalities. For segregation analysis using POINTER, selection of the sample was consistent with single as-certainment. Different population liabilities were used for probands and relatives, because affection was narrowly defined for probands and broadly defined for relatives. The hypothesis of no genetic transmission was rejected. The evidence favored autosomal dominant inheritance; recessive and polygenic models were not distinguishable. © 1992 Wiley-Liss, Inc.     

Classical Noonan syndrome is not associated with deletions of 22q11

Deletions of 22qll cause DiGeorge sequence (DGS), velo-cardio-facial syndrome (VCFS), conotruncal anomaly face syndrome, and some isolated conotruncal heart anomalies. Demonstration of a 22qll deletion in a patient with manifestations of DGS and Noonan syndrome (NS) has raised the question of whether NS is another of the chromosome 22 microdeletion syndromes. This prompted us to evaluate a cohort of patients with NS for evidence of 22qll deletions. Five of 6 NS propositi studied in our laboratory with marker N25 (D22S75) did not have a 22qll deletion. A 2-month-old infant with several findings suggestive of NS did have a 22qll deletion, suggesting that a small number of 22qll deletion propositi may present with a NS-like picture. However, most cases of NS must have another cause. © 1995 Wiley-Liss, Inc.     

Antibody-mediated neutralization of pertussis toxin-induced mitogenicity of human peripheral blood mononuclear cells

Antibody-mediated neutralization of pertussis toxin-induced proliferation of human peripheral blood mononuclear cells (PBMC) was assessed using alamarBlue and compared with results from the Chinese hamster ovary (CHO) cell assay using sera from vaccinated adults and convalescent children. Neutralization values for the CHO assay were similar for vaccinated and convalescent subjects; however. the convalescent group had higher titers in the PBMC assay. Results for pertussis toxin neutralization with the CHO assay appear to be distinct from those with the PBMC assay.     

Urachal malignant fibrous histiocytoma: a case report and review of the literature

Pathologic processes involving the urachus are usually related to inflammatory or sinofistular conditions. Neoplasms rarely arise within this structure, and when they do occur, they are typically epithelial, with mucinous adenocarcinoma being the most common. Mesenchymal lesions, both benign and malignant, have rarely been described in this location. We report the case of a 66-year-old white man who presented with a primary urachal malignant fibrous histiocytoma and died of metastatic disease 20 months after the initial diagnosis. This is an unusual case of malignant fibrous histiocytoma arising in a urachal remnant.