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BALB/c thymocytes were exposed to anti-μ serum in vitro , and both thymocytes and splenic T cells were exposed to anti-μ by long-term intensive treatment of intact animals. In all cases, the anti-μ-treated T cells could cooperate with splenocytes from nude mice in the in vitro immune response to sheep erythrocytes, indicating that cooperating T cells are not targets for immunosuppression by heterologous anti-μ antibodies.

Congenitally athymic (nude) mice have been shown to be far more sensitive than their phenotypically normal littermates to immunosuppression by anti-Ig antisera. Anti-μ suppression of nude mice was seen to result in complete and stable loss of IgM and IgA as well as severe reductions in IgG1 and IgG2 levels. Anti-α treatment of nudes resulted only in complete and stable loss of IgA; similarly, anti-γ1γ2 treatment achieved only class-specific reductions of IgG1 and IgG2 levels, but these reductions recovered slightly during suppression. Nude mice were more severely immunosuppressed than their phenotypically normal littermates upon anti-Ig treatment and demonstrated much less ability to recover from such suppressive effects. The significance of these observations regarding thymus dependency of immunoglobulin synthesis in nude mice is discussed.

Acute lymphoblastic leukaemia (ALL) has been shown to be of T-cell or undefined origin. We now describe a man of 75 years with ALL of apparent B-cell origin. Thirty-five cases of untreated ALL were studied for B-cell and twenty-four of them also for T-cell markers. In the patient with ALL of B-cell type the lymphoblasts carried mu-lambda suggesting a monoclonal origin of the malignant cells. The remaining thirty-four cases exhibited relatively normal proportions and numbers of B-lymphocyte subpopulations. Four of the twenty-four cases studied for T cells had ALL of T-cell origin. In the remaining twenty patients T lymphocytes were present, but generally in decreased numbers. The one patient with ALL of B-cell type was an elderly man, while the other thirty-four cases of T-cell or undefined origin occurred in children or younger adults. This suggests that in older patients ALL, like other lymphoid malignancies, may more often be of B-cell origin.

Heavy chain diseases (HCD) are immunoproliferative disorders characterized by the production of monoclonal immunoglobulin molecules composed of deleted heavy chains devoid of light chains. The diagnosis is established by immunoelectrophoresis (possibly combined to immunoselection) or immunofixation. The clinicopathologic features of gamma HCD are heterogenous, often somewhat similar to macroglobulinemia. Some patients show no evidence of underlying malignant lymphoproliferation. Autoimmune disorders are frequent. mu HCD is rare and often presents as chronic lymphocytic leukemia with hepatosplenomegaly and vacuolated plasma cells on bone marrow smears. Alpha chain disease is the most frequent. In its usual digestive form, the clinicopathologic pattern is uniform. The main clinical features are chronic diarrhea and severe malabsorption syndrome. At the initial stage, there is a diffuse lymphoplasmocytic infiltration of the small intestine and mesenteric nodes, sometimes reversible after treatment by antibiotics alone. At the terminal stage, a malignant lymphoma, often of immunoblastic type, occurs. The natural history and epidemiology of alpha HCD should provide insights into the pathogenesis of malignant lymphoid proliferations.