Fig 1.
Clinical and necropsy findings in the affected NOG mice xenotransplanted with tissues from human metastatic melanoma.
(A) 5-month-old female showing diffuse scaling and crusting dermatitis associated with alopecia. Note also the extreme emaciation of the animals and the complete absence of grossly detectable tumor growth in the interscapular region. Scale bar = 15 mm. (B) Total white blood cell count assessment in 7 affected NOG mice and 5 healthy matched controls from the same NOG colony. Affected NOG mice display a significant increase in white blood cell counts when compared to healthy controls (2-Tailed t-test, p = 0.012).
Fig 2.
Affected NOG mice xenotransplanted with tissue from human metastatic melanoma suffer from chronic xenogeneic GVHD-like condition initiated by co-transplanted human immune cells populating the original tumor biopsy.
(A-C) Chronic dermatitis with lichenoid interface pattern, virtually all the infiltrating immune cells co-express the T cell marker CD3 and the human-specific MHC class I molecule HLA-A. Hematoxylin an eosin (HE) staining and immunohistochemistry for CD3 and HLA-A, scale bar = 200 μm. (D-F) Dense plasma cell-rich infiltrates effacing the salivary gland parenchyma and showing prominent nuclear expression of the mature B cells/plasma cells marker BLIMP1, virtually all the infiltrating immune cells are also positive for the human-specific MHC class I molecule HLA-A. HE staining and immunohistochemistry for BLIMP1 and HLA-A, scale bar = 100 μm.
Fig 3.
Metastatic melanoma xenografts in NOG mice affected by xenogeneic GVHD are effaced by plasma cell-rich lymphoid infiltrates.
(A) Xenotransplanted metastatic melanoma is replaced by dense lymphoid infiltrates diffusely expressing human-specific MHC class I molecule HLA-A. HLA-A immunohistochemistry, scale bar = 100 μm. (B and C) Few residual groups of tyrosinase-positive melanoma cells are still detectable among the lymphoid infiltrates. Tyrosinase immunohistochemical staining, scale bar = 200 μm in B and 50 μm in C. Lymphoid infiltrates at the site of transplantation are primarily composed of MUM1p-positive plasma cells (D), CD20-positive mature B cells (E) and CD3-positive T cells. MUM1p, CD20 and CD3 immunohistochemistry, scale bar = 100 μm.
Fig 4.
NOG mice suffering from xenogeneic GVHD-like condition occasionally develop atypical plasma cell-rich lymphoid infiltrates of donor origin.
(A) Renal/perirenal plasma cell-rich infiltrates with findings of marked cytologic atypia. Hematoxylin and eosin staining (H&E), scale bar = 50 μm. (B) Human origin of the atypical lymphoid infiltrates is confirmed through the diffuse expression of human-specific MHC class I molecule HLA-A. HLA-A immunohistochemistry, scale bar = 100 μm. (C-F) Immunophenotypically the atypical lymphoid infiltrates are positive for markers of mature B cell/plasma cell differentiation including CD20, BLIMP1, MUM1p, PAX5. CD20, BLIMP1, MUM1p and PAX5 immunohistochemistry, scale bar = 100 μm.
Fig 5.
Atypical plasma cell-rich lymphoid infiltrates of donor origin in NOG mice xenotransplanted with human metastatic melanoma are monoclonal and reflect the development of post-transplant B cell/plasma cell malignancies associated with Epstein-Barr virus (EBV) reactivation.
(A) The atypical plasma cell-rich infiltrates show kappa light chain restriction suggesting monoclonal B cell/plasma cell expansion. Kappa and Lambda light immunoglobulin chains immunohistochemistry, scale bar = 100 μm. (B) Atypical lymphoid infiltrates show a clear monoclonal pattern for all IgH and IgK frameworks confirming the development of post-transplant B cell/plasma cell neoplasms, fragment lenght for each monoclonal peak is indicated (left). On the contrary, matched original human tumor biopsy displays a polyclonal pattern which is consistent with the presence of reactive B cells/plasma cells (right). Multiplex PCR for IgH and IgK rearrangements. (C) Approximately 30–40% of the atypical B cells/plasma cells populating the monoclonal lymphoid proliferation display a strong EBV-encoded RNA (EBER1-2) hybridization signal (left). On the contrary no EBER1-2 signal is observed in the original tumor biopsy (right) suggesting a post-transplant reactivation of EBV. EBER1-2 in situ hybridization, scale bar = 100 μm.