Quantitation of lymphocyte subsets by immunofluorescence flow cytometry in idiopathic dilated cardiomyopathy

Abstract

Idiopathic dilated cardiomyopathy (IDC) is a disease in which immune aberration has been postulated but not confirmed. The frequency of lymphocyte subsets was evaluated in 22 patients with IDC and in 22 blood bank control subjects, using monoclonal antibodies to cell surface markers to allow cell sorting by immunofluorescence flow cytometry. Eighteen patients with heart failure from other causes were also studied. Functional correlations were also made for the natural killer cell subset. Total T-cell frequency, determined with antihuman T (Hybritech), was similar in IDC and control groups: mean 73 ± 12% in IDC patients and 70 ± 9 % in control subjects. B-cell frequency, determined with antihuman la (Hybritech), was also similar: 36 ± 11 % in IDC patients and 31 ± 10% in control subjects. Helper T-cell frequency, identified by OKT4 (Ortho), averaged 47 ± 11 % in IDC and 44 ± 8 % in control subjects (difference not significant). Suppressor/cytotoxic T-cell frequency, established by OKT8, was the same: 28 ± 8 % in IDC and 30 ± 7 % in control subjects, although relative deficiency in suppressor functional activity has been reported in IDC. Helper to suppressor (OKT4/8) ratios, aberrant in many autoimmune diseases, did not differ significantly (IDC 1.9 ± 0.8, control 1.5 ± 0.6). Lymphocyte subsets and OKT4/8 ratio were also similar between IDC and heart failure patients. Natural killer cell frequencies, estimated using 2 antibodies (antihuman Leu-7 and Leu-11, Becton-Dickinson) were the same (9.3 ± 4.9 % in IDC patients, 9.0 ± 4.5 % in control subjects, Leu-7). In contrast, natural killer cell functional activity was decreased in the IDC group; median lymphocyte to target cell (K562 line) ratio resulting in 50% killing (L/T50) was 21 in IDC vs 10.5 in control (p <0.02). Macrophage (OKM1) frequency also did not differ. It is concluded that, despite marked cardiac dysfunction in IDC, relative percentages of lymphocyte subsets, identified by cell surface markers, are not consistently changed. In contrast, functional deficiencies (as for natural killer cells) may be present, suggesting abnormalities in activation that may respond to pharmacologic maneuvers.