Immune responses in four patients with Bloom syndrome

Immunological examinations of four patients with Bloom syndrome, belonging to two families, revealed some disturbances of the immune function. All patients had decreased levels of at least one class of immunoglobulins. The disturbances of the lymphocyte stimulation tests demonstrated a remarkable similarity in the siblings: decreased stimulation in vitro by phytohemagglutinin (PHA) and pokeweed mitogen (PWM), low responses on stimulation by specific antigens, and diminished responder capacity in mixed lymphocyte reaction (MLR) in both patients of family I: normal stimulation in vitro by PHA and PWM, high responses on stimulation by specific antigens, and diminished responder capacity in MLR in both patients of family II. This remarkable difference in expression of the defect between both families could be the expression of a genetic heterogeneity.