Bloom's syndrome. Clinical features and immunologic abnormalities of four patients
C. W. Van Kerckhove, J. L. Ceuppens, M. Vanderschueren-Lodeweyckx, E. Eggermont, S. Vertessen and E. A. Stevens
Department of Pediatrics, Faculty of Medicine, University of Leuven, Belgium.
Immune function was studied in four patients (two girls and two boys, aged
30 months to 24 years) with documented Bloom's syndrome. Three patients had
a decreased serum concentration of at least one subclass of
immunoglobulins. All had normal or elevated proportions of circulating B
cells but two of them had a decreased proportion of CD4-positive
helper-inducer T cells. We consistently found a severely impaired in vitro
proliferative lymphocyte response to the plant lectin pokeweed mitogen
(PWM). This could not be overcome by using suboptimal or supraoptimal doses
of PWM, or by adding recombinant interleukin 2. In vitro PWM-induced IgM
production was absent or low in two of the three patients studied and this
low production could not be increased by addition of hydrocortisone. T
lymphocytes responded normally to the plant lectins phytohemagglutinin and
concanavalin A. T cells preactivated with phytohemagglutinin also normally
proliferated in response to interleukin 2. It has previously been shown
that lymphocyte activation with PWM involves both B and T cells and
proceeds via an alternative pathway. The data thus indicate that patients
with Bloom's syndrome have a specific defect in this PWM-induced
alternative pathway of lymphocyte activation.
