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A 76‐year‐old man with spontaneous rupture of a hemangiosarcoma of the spleen, together with a review of 49 previously reported patients with splenic hemangiosarcoma are presented. Twenty‐three were women and 27 were men. All but 3 were adults. Fifteen were 50–59 years of age. The symptomatology was nonspecific. Three patients developed microangiopathic hemolytic anemia. Spontaneous rupture occurred in 17 cases (34%). Metastases occurred in 42 cases; they were primarily hematogenous and most often in the liver. Lymph node involvement, however, was present in 13 cases. The prognosis of untreated splenic hemangiosarcoma is poor. Three of 25 patients survived a year or more after the initial onset of symptoms. Splenectomy before rupture is advisable, since 5 of 19 patients survived at least 1–5 years. It is suggested that hemangiosarcoma be considered in patients with: 1) splenomegaly without evidence of malignant lymphoma or leukemia, 2) splenomegaly with microangiopathic hemolytic anemia, and 3) unexplained intraperitoneal hemorrhage.

Prior sc immunization of BALB/c mice with 1 mg isolated M component of MOPC-11 mouse myeloma resulted in significant relative immunity to subsequent sc or ip challenge with 10(4) living cells from the same plasmacytoma. However, challenges of 10(5) and 10(6) tumor cells overcame immune status engendered by preimmunization with M component. Despite evidence for the specificity of the immunity induced by one isolated M component as opposed to another, no clear cytotoxic antibody, cell-mediated tumor-cell lysis, or predominance of either humoral or cell-mediated immune mechanisms were demonstrated. These findings were compatible with a relatively slight tumor-specific antigenicity of M components expressed on tumor surfaces, compared with the tumor specificity of other tumor-related, cell-surface antigens.

Groups of 10-week-old female CBA/J mice were exposed in whole body fashion to 0, 5, 50, and 500 rads and sacrificed in serial fashion 1, 3, 5, 7, 9, 15, and 30 days after irradiation for morphologic evaluation of thymus, spleen, lymph node, and Peyer's patch, and assessment of the relative numbers of thymus-derived (T) and bone marrow-derived (B) cells in these tissues. The absolute and relative numbers of recirculating T and B cells mobilizable by thoracic duct cannulation were also determined and compared with similar determinations with respect to peripheral blood lymphocytes. B cell depletion occurred more quickly and was more pronounced in spleen and lymph node than T cell depletion at all three exposure doses. Depletion of T and B cells was roughly equal in peripheral blood and thoracic duct lymph. When present, regeneration of the T cell component occurred more rapidly than did B cell restoration. The latter often was incomplete at the time of the final sacrifice (day 30). PHA-responsive and Con A-responsive cells also appeared to differ with respect to the kinetics of cell death after whole body irradiation.

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