Immunological study of childhood acute ITP at onset.

We attempted to search for any specific change in the immune system during the onset of childhood acute immune thrombocytopenic purpura (ITP) in order to clarify the pathophysiology of acute ITP by examining the lymphocyte subset, lymphocyte blastogenic response, serum complements, and immunoglobulins in 18 patients with childhood acute ITP and 18 controls (control values after normalization). At the onset of acute ITP, the levels of serum complements and IgG and IgA were found to be within the normal ranges, but serum IgM levels were greater than 200 mg/dL in six cases among 18 patients. Lymphocyte blastogenic response to phytohemagglutinin (PHA) and concanavalin A (ConA) was depressed in patients relative to controls (PHA: p less than 0.05, ConA: p less than 0.01). Lymphocyte blastogenic response to pokewood mitogen (PWM) was lower than that of the control, but no statistical significance was observed. There was no difference in the proportion of CD3, CD4, CD8, SmIg, SmIgG, SmIgM, SmIgA, and SmIgD. The CD4/CD8 ratio was not different from that of controls. The proportion of CD38 was higher than that of control, but no significant difference from the control was observed. Increase in the serum IgM level and proportion of CD38 and depressed lymphocyte blastogenic response may be the influence of preceding infection. It has been reported that the CD4/CD8 ratio is depressed due to an increase in the CD8 level in acute and convalescent phases of viral infection. However, the proportion of CD8 was not necessarily increased in our patient in whom preceding infection was obvious. The immunological status of the patients with acute ITP at onset differs from that after infection.