Signal transduction by the platelet Fc receptor

We have evaluated the mechanism by which crosslinking human platelet Fc receptor (FcR) for IgG triggers platelet aggregation and the platelet release reaction. Platelet FcR was crosslinked by incubating purified human platelets with anti-FcRII monoclonal antibody and F(ab')2 anti- mouse Ig. The resultant [Ca2+]i increase, monitored by Fura-2 and measured in the absence of extracellular Ca2+, reached a peak of 750 +/- 50 nmol/L. The effects of cyclooxygenase inhibitors, aspirin and indomethacin, and a phospholipase A2 inhibitor, dibromoacetophenone, were examined. Regardless of the inhibitor, at least 25% of the [Ca2+]i increase remained. Thrombin (0.2 U/mL) stimulated an immediate [Ca2+]i increase that reached 1.95 +/- 0.8 mumol/L. The [Ca2+]i increase generated by thrombin was only slightly reduced by these inhibitors. Crosslinking the FcRII of platelets resulted in a fivefold increase in the production of [3H]inositol phosphates, (IP) which, in the absence of extracellular Ca2+ was insensitive to aspirin. The activation of a [Ca2+]i increase along with the measured increases in IP indicate that FcRII crosslinking leads to the activation of phospholipase C (PLC). In contrast to thrombin, platelet activation via FcRII depends to a large extent on arachidonic acid metabolites. However, neither cyclooxygenase nor phospholipase A2 inhibitors completely blocked FcRII-stimulated [Ca2+]i increase. These observations led us to propose that crosslinking of platelet FcRII initially activates PLC.     

Can the reading for serologic reactivity following 37 degrees C incubation be omitted?

The need to detect antibodies that agglutinate and/or hemolyze red cells (RBCs) directly at 37 degrees C, but do not react in subsequently performed indirect antiglobulin tests (IATs), is of concern relative to the streamlining and automation of antibody detection methods. To determine incidence and significance of such reactions, data from 87,480 tests, which used low-ionic-strength saline, 10-minute incubation at 37 degrees C, and anti-IgG, were analyzed for unexpected antibodies. There were 3590 positive tests, of which 475 showed reactions at 37 degrees C but not in subsequently performed IATs (37 + IAT-). Of these, 196 reactions were due to autoantibodies or other factors usually considered insignificant with respect to the survival of transfused incompatible RBCs, 176 were due to alloantibodies of questionable clinical significance (M, Lea, P1, etc.), and 103 were associated with alloantibodies of potential clinical significance (63 E, 27 K, 5 Jka, 4 D, 3 cE, and 1 C). This latter reaction was seen in 72 patients, with two 37 + IAT-antibodies occurring in each of 3 patients. Of the 75 potentially significant 37 + IAT-antibodies, 57 were seen in patients recently exposed to homologous RBCs, 13 in patients with a history of transfusion and/or pregnancy, and 5 in patients with no known exposure to homologous RBCs. IAT reactivity was observed in subsequent samples with 27 of these antibodies. The predictive value of a 37 + IAT-test was 21.7 percent for a potentially significant antibody. The incidence was 0.12 percent of all tests for unexpected antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)     

The CTLA-4 gene region of chromosome 2q33 is linked to, and associated with, type 1 diabetes. Belgian Diabetes Registry

Susceptibility to autoimmune insulin-dependent (type 1) diabetes mellitus is determined by a combination of environmental and genetic factors, which include variation in MHC genes on chromosome 6p21 (IDDM1) and the insulin gene on chromosome 11p15 (IDDM2). However, linkage to IDDM1 and IDDM2 cannot explain the clustering of type 1 diabetes in families, and a role for other genes is inferred. In the present report we describe linkage and association of type 1 diabetes to the CTLA-4 gene (cytotoxic T lymphocyte associated-4) on chromosome 2q33 (designated IDDM12). CTLA-4 is a strong candidate gene for T cell- mediated autoimmune disease because it encodes a T cell receptor that mediates T cell apoptosis and is a vital negative regulator of T cell activation. In addition, we provide supporting evidence that CTLA-4 is associated with susceptibility to Graves' disease, another organ- specific autoimmune disease.      

Sensitivity and specificity of four assays to detect human T− lymphotropic virus type I or type I/II antibodies

BACKGROUND: Assays that detect human T-lymphotropic virus type I and type II antibody (HTLV-I/II) are widely used in the routine screening of blood donors. STUDY DESIGN AND METHODS: Four commercially available anti-HTLV-I (Fujirebio and Organon Teknika) or -HTLV-I/II assays (Murex and Ortho) were evaluated in various serum panels: A) HTLV-I-positive specimens (n = 41), confirmed by Western blot and polymerase chain reaction; B) a commercially available anti-HTLV-I/II panel; C) serial dilutions of sera from HTLV-I-positive individuals (n = 30), confirmed by immunofluorescence assay and Western blot: D) serial dilutions of HTLV-II-positive blood donors (n = 20), confirmed by Western blot and polymerase chain reaction, and E) sera from first-time blood donors (n = 1055). RESULTS: All four assays elicited reactions in all 82 HTLV-I- positive samples in Panels A, B, and C. Of 32 HTLV-II-positive specimens in Panels B and D, 31 (96.9%) reacted in the Organon Teknika assay and all 32 reacted in the remaining tests. Probit analysis of test results in Panels C and D indicated that the Fujirebio test was the most sensitive assay, followed by Organon Teknika, Ortho, and Murex. The specificities of Fujirebio, Murex, Organon Teknika, and Ortho tests in 1055 first-time blood donors were 99.9, 100, 99.6, and 99.9 percent, respectively. CONCLUSION: All four studied assays for detecting HTLV-I or HTLV-I/II antibodies are appropriate as screening tests.     

Predicting zygosity in Norwegian twin pairs born 1915–1960

Present addresses of 12,752 like-sexed twin pairs born in the period 1915-1960 were identified. A questionnaire, concerning the similarity of pair members, was sent to all individuals. Responses were obtained from 83.7% of the subjects. The zygosity of 207 pairs was established by examination of genetic markers. By using discriminant analysis on the responses from this subgroup, functions were obtained for prediction of zygosity from questionnaire data. It was estimated that 2.4% of the pairs would be misclassified if the questionnaire responses from both pair members were used, and 3.9% if only the response from one of the twins was used. Accordingly, zygosity could be predicted with satisfactory reliability also for twin pairs where only one of the twins had responded. The predicted percentage of monozygotic (MZ) pairs among pairs where one or both twins had responded, was 39.4 (4,402/11,175). The percentage of MZ pairs was significantly lower (34.5) in death-discordant pairs than in pairs in which both twins were alive (39.6). The zygosity questionnaire data are sufficient to adequately score twin pairs for zygosity in the great majority of cases.     

Chronic oral inflammation and the progression of periodontal pathology in the third molar region.

PURPOSE: To assess the association between risk markers of chronic oral inflammation and changes over time in periodontal probing depth (PD) in the third molar region, the distal of a second molar, or around a third molar. SUBJECTS AND METHODS: The data from these analyses are part of a study of subjects enrolled with 4 asymptomatic third molars with adjacent second molars in an institutional review board-approved longitudinal trial. Full-mouth periodontal probing was conducted at enrollment and follow-up. Enrollment levels of periodontal pathogens and gingival crevicular fluid inflammatory mediators were assayed as indicators of the degree of oral inflammation. Subjects were categorized as those who had at least a 2 mm change in periodontal PD between baseline and follow-up in the third molar region and those who did not. The relationship between aggregated subject baseline PD, levels of periodontal pathogens, and gingival crevicular fluid IL-1 beta, and the proportion of subjects with changes in PD >or=2 mm versus those with PD <2 mm were compared with Cochran-Mantel-Haenzsel statistics. Level of significance was set at 0.05. Risk assessment models for a change in PD >or=2 mm were developed using logistic regression analysis. RESULTS: Twenty-four percent of 254 subjects exhibited a change in PD from baseline to follow-up of >or=2 mm in the third molar region. Of these, 95% had a baseline PD of >or=4 mm. Both high (>or=10(5)) "orange" and "red" complex bacteria and PD of >or=4 mm detected at enrollment were significantly associated with a change in PD >or=2 mm. Odds of a change in PD >or=2 mm were increased if baseline pathogen levels were >or=10(5) or a PD of >or=4 mm was detected at enrollment. CONCLUSION: Our findings are consistent with chronic oral inflammation leading to a progression of periodontal disease in the third molar region.     

Fine-needle aspiration cytology of the adrenal gland. Fifty biopsies in 48 patients.

Fine-needle aspiration biopsy of 50 adrenal masses from 48 patients was performed between 1984 and 1991. The series consisted of 28 males and 20 females, with an age range of 12 months to 79 years (mean age, 55 years). Clinical and/or pathologic follow-up was available in 37 patients. Fine-needle aspiration was diagnostic in all 29 malignant cases having follow-up, with no false-positive diagnoses. There were six primary malignancies (three neuroblastomas, two pheochromocytomas, and one adrenal cortical carcinoma) and 23 metastatic lesions. Of these, the lung was the most frequent primary malignancy (60%), followed by melanoma and renal cell carcinoma (8.6% each). The remaining nonmalignant fine-needle aspiration diagnoses were adrenal cortical neoplasms (most likely adenoma), adrenal cortical hyperplasia, myelolipoma, benign adrenal tissue, and abscess. Based on clinical follow-up, three other adrenal adenomas were not diagnosed by fine-needle aspiration. Six biopsy specimens (12%) were insufficient for diagnosis. Ancillary studies including electron microscopy and/or immunocytochemistry were performed on 13 malignant aspirates and provided additional confirmation of the cytology diagnosis in 12 cases. This study confirms that fine-needle aspiration is a sensitive and highly specific procedure for the evaluation of primary and metastatic malignancies involving the adrenal gland. The technique is less useful in the workup of benign processes but, in some instances, can provide specific diagnostic information.