F. Facchetti

Rabbit Monoclonal Antibodies A Comparative Study Between a Novel Category of Immunoreagents and the Corresponding Mouse Monoclonal Antibodies

Rabbit monoclonal antibodies (RabMAbs) represent a novel category of immunoreagents that may combine the best properties of both mouse monoclonal antibodies (MMAs) and of rabbit antisera. In the attempt to verify the performance of this new class of antibodies on paraffin-embedded tissue, RabMAbs against estrogen receptor, progesterone receptor, Ki-67, cyclin D1, CD3, CD5, CD23, and synaptophysin were tested on several tumor types as well as normal tissues. The results were compared with those obtained with classic MMAs against the same antigens. RabMAbs appear to offer increased sensitivity with no apparent loss of specificity. On routine use they permit higher working dilutions (5 to 10 times on average), allowing significant improvement in terms of laboratory efficiency. The robustness of RabMAbs is further proved by the fact that in some instances optimal staining can be obtained even without antigen retrieval. In consideration of the high performance observed, routine use of RabMAbs may contribute significantly to standardize diagnostic immunohistochemical procedures.

Myeloperoxidase Expression by Histiocytes in Kikuchi's and Kikuchi-Like Lymphadenopathy

Forty-five examples of Kikuchis lymphadenitis (KL), 5 Kikuchi-like lupus erythematosus lymphadenopathies, 25 nonnecrotizing lymphadenitidies (5 toxoplasmic, 5 sarcoid-like, 6 dermatopathic, 4 suppurative, 3 tubercular, 2 with sinus histiocytosis), 4 examples of hyaline-vascular Castleman disease (CD), 2 plasmacytoid monocyte tumors (PM-Ts), and 61 accessory cell neoplasms were studied by a panel of antibodies, including the PG-M1 (against a macrophage-restricted CD68 epitope) and a polyclonal anti-myeloperoxidase (MPO). In KL and Kikuchi-like lupus erythematosus lymphadenopathies, 25 to 75% of CD68(+) histiocytes co-expressed MPO. This did not occur in nonnecrotizing lymphadenitidies and accessory cell neoplasms. MPO(+)/CD68(+) elements corresponded to nonphagocytosing mononuclear cells and some crescentic macrophages and phagocytosing histiocytes. Typical PMs were MPO(-)/CD68(+) in all cases, including CD and PM-T. Our observations suggest that in KL and KL-like lymphadenopathies: 1) MPO(+)/CD68(+) blood monocytes might be attracted into tissues because of the lack or paucity of granulocytes and the need of MPO for oxidative processes; 2) PMs are more likely to be involved in the cytotoxic immune reaction than in phagocytic phenomena; 3) the peculiar phenotype of the histiocytic component can be usefully used for the differentiation from malignant lymphoma and PM-T.

Rabbit Monoclonal Antibodies

Rabbit monoclonal antibodies (RabMAbs) represent a novel category of immunoreagents that may combine the best properties of both mouse monoclonal antibodies (MMAs) and rabbit antisera. In the attempt to verify the performance of this new class of antibodies on paraffin-embedded tissue, RabMAbs against estrogen receptor, progesterone receptor, Ki-67, cyclin D1, CD3, CD5, CD23, and synaptophysin were tested on several tumor types as well as normal tissues. The results were compared with those obtained with classic MMAs against the same antigens. RabMAbs appear to offer increased sensitivity with no apparent loss of specificity. On routine use they permit higher working dilutions (5 to 10 times on average), allowing significant improvement in terms of laboratory efficiency. The robustness of RabMAbs is further proved by the fact that in some instances optimal staining can be obtained even without antigen retrieval. In consideration of the high performance observed, routine use of RabMAbs may contribute significantly to standardize diagnostic immunohistochemical procedures.

Neutrophilic Eccrine Hidradenitis in a Healthy Woman

Dr. Ausilia M. Manganoni, Divisione Dermatologia, Spedali Civili, I-25125 Brescia (Italy) #3⁄8 • ‘% 2 days duration. The patient had received no drugs and was in good health. Physical examination revealed painful edematous red plaques on the plantar areas, suggesting chilblains. The skin lesions resolved without sequelae within 3 weeks. The histologic examination revealed a superficial and deep inflammatory infiltrate in the dermis predominantly composed of neutrophils. The heavy infiltrate surrounded the eccrine coil and the dermal eccrine ducts and occasionally reached the acrosyringium (fig. 1). Necrosis and vacuolar degeneration of eccrine coil cells were also noted (fig. 2). Focal abscesslike accumulations of neutrophils were found both in the superficial and the deep parts of the dermis. Vessels were occasionally surrounded by neutrophils, but endothelial neFig. 1. NEH: an infiltrate predominantly of neutrophils is seen around the eccrine coil, the dermal eccrine ducts and reaching the acrosyringium. Neutrophilic eccrine hidradenitis (NEH) has been described in patients receiving chemotherapy [1-4]. To the best of our knowledge, we report the second case of NEH in an otherwise healthy individual. A 23-year-old Hispanic waitress was hospitalized for evaluation of slight tender skin lesions on the plantar regions of both feet of

Burkitt lymphoma beyond MYC translocation: N-MYC and DNA methyltransferases dysregulation.

BackgroundThe oncogenic transcription factor MYC is pathologically activated in many human malignancies. A paradigm for MYC dysregulation is offered by Burkitt lymphoma, where chromosomal translocations leading to Immunoglobulin gene-MYC fusion are the crucial initiating oncogenic events. However, Burkitt lymphoma cases with no detectable MYC rearrangement but maintaining MYC expression have been identified and alternative mechanisms can be involved in MYC dysregulation in these cases.MethodsWe studied the microRNA profile of MYC translocation-positive and MYC translocation-negative Burkitt lymphoma cases in order to uncover possible differences at the molecular level. Data was validated at the mRNA and protein level by quantitative Real-Time polymerase chain reaction and immunohistochemistry, respectively.ResultsWe identified four microRNAs differentially expressed between the two groups. The impact of these microRNAs on the expression of selected genes was then investigated. Interestingly, in MYC translocation-negative cases we found over-expression of DNA-methyl transferase family members, consistent to hypo-expression of the hsa-miR-29 family. This finding suggests an alternative way for the activation of lymphomagenesis in these cases, based on global changes in methylation landscape, aberrant DNA hypermethylation, lack of epigenetic control on transcription of targeted genes, and increase of genomic instability. In addition, we observed an over-expression of another MYC family gene member, MYCN that may therefore represent a cooperating mechanism of MYC in driving the malignant transformation in those cases lacking an identifiable MYC translocation but expressing the gene at the mRNA and protein levels.ConclusionsCollectively, our results showed that MYC translocation-positive and MYC translocation-negative Burkitt lymphoma cases are slightly different in terms of microRNA and gene expression. MYC translocation-negative Burkitt lymphoma, similarly to other aggressive B-cell non Hodgkin’s lymphomas, may represent a model to understand the intricate molecular pathway responsible for MYC dysregulation in cancer.

Specific skin infiltration as first sign of chronic myelomonocytic leukemia with an unusual phenotype

A patient who had a plaque on his forehead as the first sign of chronic myelomonocytic leukemia (CMML) is described. Histologic studies, which formerly led to the misdiagnosis of non-Hodgkins lymphoma, revealed CMML with an unusual phenotype. This represents a rare type of CMML for the following reasons: (1) specific cutaneous involvement is rarely the first sign of CMML; (2) the unique phenotype was detected by immunohistology on lesional skin, specifically, the leukemic infiltrate was CD4-positive and notably negative for CD15, the pan myeloid/monocytic marker.