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Antibodies targeting T cells and B cells are increasingly used for immunosuppression in clinical transplantation. However, the impact of T-cell depletion by antibodies on B-cell homeostasis is poorly understood. Using a mouse model of allosensitization with skin allograft, we investigated whether targeting T cells by anti-CD3ε alters peripheral B-cell homeostasis and alloantibody responses following B-cell depletion by anti-CD20. We found that anti-CD3ε induced a discrete B220(lo), but not a conventional B220(hi) subset, in the spleens of the allosensitized mice 14 days after anti-CD20 treatment. The splenic B220(lo) cells were refractory to anti-CD20 depletion. Flow cytometry revealed that the splenic B220(lo) cells were phenotypically similar to the B220(lo) AA4.1(+) CD23(-) sIgM(lo) sIgD(-) developing B cells (pre-B to immature B) normally presented in the bone marrow. Despite the presence of the splenic B220(lo) cells, mice treated with combined anti-CD3ε/CD20 produced limited alloantibodies in response to the primary skin allografts. Alloantibody production increased significantly in the mice following re-immunization by donor-specific splenocytes. We conclude that anti-CD3ε can induce an expansion of B220(lo) B cells in the spleens after B-cell depletion by anti-CD20. These B cells are not producing alloantibodies, but re-immunization of the mice with alloantigen leads to risk of alloantibody response.

Peribiliary cysts are cystic dilatations of peribiliary glands in the liver. They are present in ~50% of cirrhotic patients, but are underrecognized because they are usually asymptomatic and rarely present as obstructive jaundice. A 63-year-old male with hepatitis C cirrhosis, awaiting liver transplantation, had a new finding of intrahepatic dilatation on magnetic resonance imaging. This was initially concerning for cholangiocarcinoma, but was ultimately diagnosed as peribiliary cysts. Peribiliary cysts can imitate cholangiocarcinoma on imaging. Therefore, awareness of this condition is essential because misdiagnosis may lead to inappropriate delay or denial for liver transplantation. The ideal imaging modalities to identify peribiliary cysts are magnetic resonance cholangiography and drip infusion cholangiographic computed tomography, though hepatic dysfunction may limit the usefulness of the latter. Peribiliary cysts should be considered in cirrhotic patients with cholestasis, biliary dilatations and negative biopsy of the biliary system for malignancy.

An in vivo assay to quantify simultaneously two important components of hepatic reticuloendothelial system (RES) function—clearance and phagocytic killing—was developed in the rat. Intravenously injected E. coli labeled with Na51Cr and 5-[123I]-iodo-2′-deoxyuridine were cleared rapidly from the blood primarily by the liver. While hepatic 51Cr levels remained stable for 24 h following inoculation and provided a reliable measurement of clearance, hepatic 125I decreased over time. Hepatic 125I, calculated by sampling whole liver homogenates, accurately reflects the number of viable bacteria recovered from quantitative cultures of the same homogenates, thus validating this assay as a measure of bacteria killing. Pre-treatment of rats with substances previously shown to affect RES function (gadolinium, zymosan, and sheep erythrocytes) were found to selectively modulate clearance and/or killing. The correlation between hepatic isotope levels and viable hepatic bacteria, the gold standard for assessing the capacity of the liver to remove organisms from the blood and kill them, was preserved under conditions of up- and down-regulation of RES function. The ability to quantitatively discriminate two distinct components of the hepatic RES should provide a useful tool for future investigations of altered RES function. J. Leukoc. Biol. 55: 248–252; 1994.