Autoantibodies to IA-2 and GAD65 in patients with type 2 diabetes mellitus of varied duration: prevalence and correlation with clinical features.

OBJECTIVE: To determine the prevalence of autoantibodies to IA-2 (IA-2Ab) and glutamic acid decarboxylase (GADAb) in type 2 diabetes, their relationship to disease duration, and their importance in management decisions. METHODS: We undertook a study of 101 patients with type 2 diabetes (defined as nonketotic hyperglycemia at diagnosis) of varied duration (median, 4 years). Results were compared with those from 36 patients with type 1 diabetes also of varied duration (median, 2 years). IA-2Ab and GADAb were measured by radioligand-binding assays with use of in vitro-synthesized, 35S-labeled antigens. RESULTS: Of the 101 patients with type 2 diabetes, 20 (20%) were positive for GADAb; only 4 of these 20 were positive for IA-2Ab. In comparison, 75% of patients with type 1 diabetes were positive for GADAb, IA-2Ab, or both (P<0.0001). The coincidence of IA-2Ab positivity in GADAb-positive patients with type 2 diabetes was significantly lower than in patients with type 1 diabetes (20% versus 73%, respectively; P = 0.002). All four IA-2Ab- and GADAb-positive patients with type 2 diabetes required insulin and were younger than those positive for GADAb alone (P = 0.018). GADAb positivity in patients with type 2 diabetes was highly associated with insulin requirement (P = 0.004), with an odds ratio of 5.8 in predicting insulin dependence. Among patients with type 2 diabetes receiving insulin therapy, disease duration was significantly shorter (P = 0.025) and body mass index was significantly lower (P<0.001) in GADAb-positive versus GADAb-negative patients. In contrast to type 1 diabetes, in which GADAb values were negatively correlated with disease duration (r = -0.34; P = 0.044), no significant correlation with disease duration was observed in type 2 diabetes (r = -0.166; P = 0.48). CONCLUSION: Irrespective of duration of disease, measurement of IA-2Ab and GADAb can help to identify those patients with type 2 diabetes most likely to require insulin therapy.

Epitope heterogeneity of thyrotropin receptor-blocking antibodies in Graves' patients as detected with wild-type versus chimeric thyrotropin receptors.

The stable transfectants of wild-type (W25) and mutant thyrotropin-receptor (TSH-R) allow detection of the bioactivities of TSH-R antibodies in Graves' patients. A mutant Chinese hamster ovary (CHO) cell line (Mc1+2) transfected with a chimeric construct, where residues 8 to 165 of the TSH-R are replaced with residues 10 to 166 of the lutropin/choriogonadotropin (LH/CGR) receptor, lacks the cyclic adenosine monophosphate (cAMP) response to most thyrotropin stimulating antibodies (TSAb), yet retains the response to TSH and acquires the response to LH/CG. We compared Mc1+2 cells with wild-type W25 cells for their ability to detect TSAb as well as thyrotropin-blocking antibodies (TBAb) in Graves' sera. Eighteen normal and 39 Graves' sera were tested for TSAb and TBAb levels by in vitro bioassays using W25 and Mc1+2 cells. In addition, these sera were also tested for thyrotropin-binding inhibitory activity (TBII) by a radioreceptor assay. Eighteen (47%) Graves' sera had TBAb activity measured with W25 cells but not with Mc1+2 cells. These TBAbs were, therefore, a population of antibodies with functional epitopes on the N-terminus of the extracellular domain. This TBAb activity by W25 cells exhibited a high degree of correlation with TBII levels by a radioreceptor assay (r = 0.70, p = 0.001). Ten (25.6%) Graves' sera had positive TBAb activity in both W25 and Mc1+2 cells; moreover, their activity in both assays was similar (r = 0.83, p < 0.001). The TBAb activity in these sera, however, did not correlate with TBII activity. Eleven (28%) Graves' sera had no TBAb activity. Overall, thyroid-stimulating antibodies were detected in 87% and 28% of the 39 Graves' sera by W25 and Mc1 +2 cells, respectively. Thus, using the 2 cell lines, at least 2 distinct populations of TBAbs were detected. One is detected in a similar fashion by both W25 and Mc1+2 cell lines and likely interacts with the epitopes residing in the unaltered C-terminus of the TSH-R. The other is reactive in W25 cells only, indicating the loss of TBAb epitope in the chimeric receptor located in the N-terminus of the TSH-R. Furthermore, our results indicate that the TBAb binding epitope in 8-165 residues of the native TSH-R is highly associated with TBII activity in Graves' disease. These results indicate that patients with Graves' disease harbor TBAbs with epitope heterogeneity and favor the notion that there are different sites and mechanisms by which TBAbs act in Graves' patients. It remains to be determined whether or not TBAb subtyping will have a useful predictive role in the management of patients with Graves' disease.

Combined nested RT-PCR assay for prostate-specific antigen and prostate-specific membrane antigen in prostate cancer patients: correlation with pathological stage.

Nested reverse transcription (RT)-PCR for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM) can detect circulating prostatic cells in patients with prostate cancer. We evaluated the role of a combined screening approach for PSA and PSM in prostate cancer staging. We examined the peripheral blood samples from 136 patients with adenocarcinoma of the prostate (PCA), 15 patients with benign prostatic hyperplasia, 15 normal male subjects, and 5 female subjects. The controls (benign prostatic hyperplasias, normal males, and normal females) were negative for both PSA and PSM. In patients with metastatic PCA (n = 11), 100% were positive by combined PSA/PSM (64% by PSA and 91% by PSM). In biochemical failure PCA patients (n = 18), 39% were positive by PSM, compared to only 6% by PSA. In patients with clinically localized PCA (n = 107), 48% were positive by combined PSA/PSM approach (43% by PSM and 14% by PSA). These results show that PSM is a more sensitive marker than PSA in detecting circulating prostatic cells (P < 0.0001). We correlated preoperative RT-PCR results with final pathological stages in 67 prostatectomy patients. RT-PCR positivity was 81.5% in patients with non-organ-confined disease versus 37.5% in organ-confined disease (P = 0.001). PSA/PSM RT-PCR had an odds ratio of 7.3 (95% confidence interval, 2.3-23.4; P = 0.001) in predicting tumor extracapsular extension. PSA/PSM RT-PCR was a better predictor of tumor extracapsular extension than initial serum PSA, clinical stage, and biopsy Gleason score. Our data show that PSA/PSM nested RT-PCR may provide the staging information unavailable from the current modalities. The ultimate impact of this technique in the management of patients with prostate cancer will require continued investigation.