Down-regulation of CD3 antigen on adult T cell leukemia cells

The immunological abnormality of T lymphocytes in patients with adult T cell leukemia (ATL) is characterized by the abnormal enhanced expression of the 55 kDa chain of the receptor for interleukin 2 (IL-2R/p55) (Tac), and down-regulation of CD3 antigen. Using serum and culture supernatants of leukemic cells from ATL patients (Group A) whose CD3 expression was down-regulated and those whose CD3 was not low (Group B), the possible mechanism of CD3 down-regulation on ATL cells was investigated. When PBMC from normal individuals were cultured with sera from ATL patients for 24 hrs, CD3 expression revealed by means of fluorescent intensity (MFI) was down-regulated by sera from ATL patients in Group A (MFI: Pt.1 = 51.6 +/- 4.5, Pt.2 = 48.0 +/- 6.9, Control = 96.5 +/- 6.6), not by sera from patients in Group B (MFI: Pt.3 = 105.5 +/- 7.9, Pt.4 = 102.5 +/- 8.3, Control = 96.5 +/- 6.6). When normal PBMC were cultured with supernatants of leukemic cells from ATL patients in Group A, the same CD3 down-regulating activity was also detected (MFI: Pt.1 = 78.0 +/- 10.2, Pt.2 = 70.6 +/- 8.7, Control = 94.0 +/- 6.6). By using gel-chromatography, the fractionated supernatants from ATL patients in Group A decreased CD3 expression of normal PBMC significantly (MFI: Pt.1 = 22.9 +/- 5.8, Pt.2 = 28.8 +/- 7.4, Control = 92.1 +/- 9.6).(ABSTRACT TRUNCATED AT 250 WORDS)