Low bcl-2 expression and increased spontaneous apoptosis in T-lymphocytes from newly-diagnosed IDDM patients.
The bcl-2 gene product has been shown to regulate apoptotic cell death, and its dysregulation has been shown to induce several abnormalities in the immune system. No data exist regarding bcl-2 expression in autoimmune diseases, such as human insulin-dependent diabetes mellitus (IDDM). We investigated bcl-2 protein expression by testing T lymphocytes from 15 newly-diagnosed (< 3 weeks) IDDM patients in comparison to 10 age-matched control subjects. The expression of bcl-2 on CD3+ lymphocyte subsets was investigated after membrane permeabilization by two- or three-colour immunofluorescence. When the percentage and mean fluorescence intensity (MFI) of bcl-2+/CD3+ cells from normal individuals and patients were compared, we found that bcl-2 expression within the CD3+ and CD4+ CD45R0+ T-cell populations was reduced significantly in IDDM patients (46.8 +/- 15.4 vs 79.6 +/- 11.7; 25.7 +/- 3.8 vs 47.15 +/- 5.7, respectively; p < 0.001). To establish whether low bcl-2 expression in T cells from newly-diagnosed patients reflects their susceptibility to death by an apoptotic process, we also evaluated DNA staining with propidium iodide in CD3+ lymphocyte suspension after a (24-72 h) culture period (spontaneous apoptosis). We found that IDDM patients have higher levels of spontaneous apoptosis (mean +/- SEM: 24 h = 4.6 +/- 0.8; 48 h = 9.9 +/- 1; 72 h = 12.8 +/- 1.1) than control subjects (24 h = 1.8 +/- 0.4; 48 h = 4.6 +/- 0.4; 72 h = 5.7 +/- 0.3; p < 0.02-0.001). Our study suggests that recent onset IDDM is characterised by reduced bcl-2 expression, which in turn may be associated with the increased spontaneous apoptosis we observed.
Giordano
C
C
Laboratory of Immunology, Endocrinology Section, Institute of Clinica Medica, University of Palermo, Italy.
Stassi
G
G
Todaro
M
M
De Maria
R
R
Richiusa
P
P
Scorsone
A
A
Giordano
M
M
Galluzzo
A
A
D000293:Adolescent; D000328:Adult; D015703:Antigens, CD / Q000097:blood; D017209:Apoptosis; D001323:Autoantibodies / Q000097:blood; D001786:Blood Glucose / Q000032:analysis; D017252:CD3 Complex / Q000097:blood; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000235:genetics* / Q000276:immunology*; D005190:Family; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D008297:Male; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2; D012016:Reference Values; D012307:Risk Factors; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*
D015703:Antigens, CD; D001323:Autoantibodies; D001786:Blood Glucose; D017252:CD3 Complex; D006442:Glycated Hemoglobin; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C024211:islet cell antibody