Flow Cytometric Immunophenotype of Canine Lymph Node Aspirates

Flow Cytometric Assessment of Ki-67 Expression in Lymphocytes From Physiologic Lymph Nodes, Lymphoma Cell Populations and Remnant Normal Cell Populations From Lymphomatous Lymph Nodes

Recent literature suggests conventional flow cytometric (FCM) immunophenotyping complemented by Ki-67 FCM assessment as a reliable tool to classify canine lymphomas. Ki-67 expression assessed by FCM is rarely reported in canine lymphoma cases and reference data for normal canine lymph nodes are missing. Moreover, nothing is known about the Ki-67 expression within the occasionally observed remnant cell population within the gates of normal lymphocytes in lymphoma cases. Aim of this study was to compare flow cytometric Ki-67 expression of lymphocyte populations from normal canine lymph nodes, lymphoma cells from World-Health-Organisation (WHO) classified lymphoma patient samples and their neighboring normal remnant cell population. Cryopreserved lymphocyte cell suspensions from normal lymph nodes from eight dogs free of lymphoma served as reference material. Fourteen cases diagnosed by cytology, FCM, clonality testing, histopathology including immunohistochemistry consisting of 10 DLBCL, 1 MZL, 1 PTCL and 2 TZL showed a residual small lymphocyte population and were investigated. The Ki-67 expression in normal canine lymphoid tissue was 3.19 ± 2.17%. Mean Ki-67 expression in the malignant cell populations was 41 ± 24.36%. Ki-67 positivity was 12.34 ± 10.68% in the residual physiologic lymphocyte population, which otherwise exhibited a physiologic immunophenotype pattern. This ratio was equivalent (n = 3) or lower (n = 11) than the Ki-67 expression of the malignant cell population within the sample. This is the first report of FCM derived Ki-67 expression combined with immunophenotype patterns in normal canine lymph nodes, compared with lymphoma cell populations and residual normal cell populations of lymphoma cases diagnosed by state of the art technology.

Flow Cytometry in the Diagnosis of Canine B-Cell Lymphoma

B cell lymphoma (BCL) is a heterogeneous group of lymphoid malignancies which comprise the majority of canine lymphomas. Diffuse large B cell lymphoma is the most common lymphoma subtype in dogs but other subtypes (e.g., marginal zone lymphoma, follicular lymphoma, mantle cell lymphoma, and others) have been described. This review aims to explore the use of flow cytometry to refine the diagnosis of canine BCL. Particular emphasis will be given to the possible identification of peculiar immunotypes, putative prognostic markers, staging and minimal residual disease.

Immunophenotyping: Application to Safety Assessment

A continuing education course entitled “What You Always Wanted to Know About Immunotoxicology in Pharmaceutical Development…But Were Afraid to Ask” was offered at the Society of Toxicologic Pathology (STP) 36th annual symposium in Montreal. This article summarizes some key points made during the presentation dedicated to immunophenotyping. It describes how clusters of differentiation (CDs) are well-defined antigens used to characterize cell subsets, and how lymphocyte subsets in humans and different rodent and nonrodent species can be defined by detection of various combinations of CDs. It provides an overview of immunophenotyping study design considerations and applications to safety assessment.

Composition of lymphocyte subpopulations in normal canine lymph nodes

BACKGROUND

Flow cytometric immunophenotyping of lymph node aspirates has become a standard practice of canine lymphoma diagnostic workup. Ultimately, the combination of flow cytometry data, histopathology, and clinical signs allows consensus classification, and improves prognostic accuracy and therapeutic approaches.

OBJECTIVES

Although there is a growing body of information regarding lymphocyte population subsets in various types of lymphoma, only few studies provide information regarding the composition of the normal canine lymph node. The aim of this prospective study was to establish exploratory reference data for lymphocyte subpopulations in normal canine lymph nodes using an extended panel of antibodies.

METHODS

Popliteal lymph nodes excised from normal dogs were analyzed by cytology, multi-color flow cytometry using 11 different canine-specific and anti-human cross-reactive monoclonal antibodies, and polymerase chain reaction for antigen receptor rearrangement (PARR).

RESULTS

Subpopulations from lymph nodes of 26 dogs were classified according to the following positive antibody reactions: CD11a(+) 92.2 ± 12.3%, CD3(+) 55.0 ± 14.1%, CD3-12(+) 57.3 ± 14%, CD5(+) 52.3 ± 12.7%, CD21(+) 33.9 ± 11.8%, CD79αcγ(+) 46.9 ± 14.8%, CD56(+) 4.9 ± 5.9%, and CD14(+) 5.5 ± 6.8%. There were 58.7 ± 9% CD4(+) and 21.3 ± 7.8% CD8(+) cells inside the gate of CD3(+) cells. Cytology revealed a mixed population of mostly lymphoid cells in all samples. The absence of a monoclonal or oligoclonal neoplastic population was confirmed by PARR.

CONCLUSION

This study establishes for the first time flow cytometry data of lymphocyte populations in a larger group of normal canine lymph nodes, including populations positive for some new antibodies against CD3-12, CD5, CD11a, CD56, and CD79αcy.

Detection of clonal antigen receptor gene rearrangement in dogs with lymphoma by real-time polymerase chain reaction and melting curve analysis

Background

Molecular techniques that detect canine lymphoma cells by their clonal antigen receptor gene rearrangement play an increasing role for diagnosis as well as for monitoring minimal residual disease during and after cytostatic therapy. However, the methods currently available are time-consuming and/or cost-intensive thus impeding the use in clinical routine. The aim of the present study was to develop and evaluate a real-time polymerase chain reaction (PCR) with subsequent melting curve analysis (MCA) for the detection of clonally rearranged antigen receptor genes in dogs with B and T cell lymphoma on non formalin-fixed and paraffin-embedded lymph node samples.

Results

In lymph node aspirates from 30 dogs with multicentric B cell lymphoma, real-time PCR with MCA detected clonal rearrangement in 100% and conventional PCR with polyacrylamide gel electrophoresis (PAGE) in 93% of samples. Both methods correctly identified clonality in 80% of lymph node aspirates of 10 dogs with T cell lymphoma. None of the two PCR systems detected clonal rearrangement in samples from 9 dogs with lymph node hyperplasia. Using a dilutional series with regular lymphoid desoxyribonucleic acid (DNA), detection limits of lymphoma DNA were as low as 0.8% and 6.25% for B and T cell clonal rearrangement with real-time PCR and MCA and at 3.13% and 12.5% with the conventional system. Median absolute detection limits of lymphoma DNA were shown to be at 0.1 ng and 1 ng for the B and T cell immunophenotype with the real-time PCR system and at 10 ng each with conventional PCR and PAGE.

Conclusions

Real-time PCR with MCA is a convenient and reliable method with a good analytical sensitivity. Thus, the method may assist the detection of clonal antigen receptor gene rearrangement in canine lymphoma patients in a clinical setting also in the presence of small amounts of neoplastic cells.

Rapid, effective and user-friendly immunophenotyping of canine lymphoma using a personal flow cytometer

BACKGROUND

Widespread use of flow cytometry for immunophenotyping in clinical veterinary medicine is limited by cost and requirement for considerable laboratory space, staff time, and expertise. The Guava EasyCyte Plus (Guava Technologies, Hayward, CA, US) is the first, personal, bench-top flow cytometer designed to address these limitations.

OBJECTIVE

The aim of this study was to adapt the immunohistochemical protocol used for immunophenotyping of canine lymphoma to the personal flow cytometer for rapid, effective and user-friendly application to the diagnosis and prognosis of canine lymphoma and to demonstrate its practicality for widespread veterinary application. Performance of the personal flow cytometer for immunophenotyping T and B lymphocytes in blood and lymph nodes from normal dogs and dogs with lymphoproliferative disease, was assessed using only two monoclonal antibodies (against CD3 and CD21), and by comparison with analysis using two conventional flow cytometers.

METHODS

26 dogs with lymphoproliferative disease (23 with lymphoma, 3 with lymphocytic leukaemia) were studied along with 15 controls (2 non-lymphoma lymph nodes and 13 non-leukemic bloods. Lymphocytes were immunostained with fluorescent-labeled, monoclonal antibodies against CD3 and CD21. To assess the effectiveness of the personal flow cytometer in discrimination between T and B cell immunophenotypes, T and B cell counts for half the samples (14 blood and 11 lymph node) were also determined using the same method and conventional flow cytometers (FACSCalibur, Cyan Dako). To assess the effectiveness of the personal flow cytometer in discriminating between leukocyte types, lymphocyte differential counts were determined for 21 blood samples and compared with those from automated hematology analyzers (CELL-DYN 3500, n=11 and ADVIA 2120, n=10). Quality and sub-cellular distribution of immunostaining was assessed using fluorescence microscopy.

RESULTS

The protocol for immunophenotyping took 2 to 3 hours to complete from the point of receipt of sample to reporting of immunophenotype. The personal flow cytometer differential lymphocyte counts correlated highly (n=20; r=0.97, p<0.0001) with those of automated haematology analyzers. The personal flow cytometer counts consistently, but mildly, underestimated the percentages of lymphocytes in the samples (mean bias of -5.3%.). The personal flow cytometer immunophenotype counts were indistinguishable from those of conventional flow cytometers for both peripheral blood samples (n=13; r=0.95; p<0.0001; bias of -1.1%) and lymph node aspirates (n=11,r=0.98; p<0.001; bias of 1%). All but one leukemic and one lymphomatous lymph node sample, out of 26 samples of dogs with lymphoproliferative disease analyzed, could be immunophenotyped as either B or T cells.

CONCLUSIONS

We conclude that use of only 2 monoclonal antibodies is sufficient for immunophenotyping most cases of canine lymphoma by flow cytometry and enables rapid immunophenotyping. The personal flow cytometer may be as effectively used for immunophenotyping canine lymphoma as conventional flow cytometers. However, the personal flow cytometer is more accessible and user-friendly, and requires lower sample volumes.

Flow cytometric evaluation of peripheral blood and bone marrow and fine-needle aspirate samples from multiple sites in dogs with multicentric lymphoma

OBJECTIVE

To determine whether the extent of disease in dogs with lymphoma can be assessed via flow cytometry and to evaluate the suitability of fine-needle aspirates from the liver and spleen of dogs for flow cytometric examination.

ANIMALS

44 dogs with multicentric B-cell (n = 35) or T-cell lymphoma (9) and 5 healthy control dogs. Procedures-Peripheral blood and bone marrow samples and fine-needle aspirates of lymph node, liver, and spleen were examined via flow cytometry. Logarithmically transformed T-cell-to-B-cell percentage ratio (log[T:B]) values were calculated. Thresholds defined by use of log(T:B) values of samples from control dogs were used to determine extranodal lymphoma involvement in lymphoma-affected dogs; results were compared with cytologic findings.

RESULTS

12 of 245 (5%) samples (9 liver, 1 spleen, and 2 bone marrow) had insufficient cellularity for flow cytometric evaluation. Mean log(T:B) values of samples from dogs with B-cell lymphoma were significantly lower than those of samples from the same site in dogs with T-cell lymphoma and in control dogs. In dogs with T-cell lymphoma, the log(T:B) of lymph node, bone marrow, and spleen samples was significantly higher than in control dogs. Of 165 samples assessed for extranodal lymphoma involvement, 116 (70%) tested positive via flow cytometric analysis; results agreed with cytologic findings in 133 of 161 (83%) samples evaluated via both methods.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that flow cytometry may aid in detection of extranodal lymphoma involvement in dogs, but further research is needed. Most fine-needle aspirates of liver and spleen were suitable for flow cytometric evaluation.

High agreement of routine cytopathology and immunocytochemistry in canine lymphomas

The aim of this study was to compare the concordance of immunophenotype established with routine cytopathology (slides stained with Giemsa solution) and immunocytochemistry according to CD3 and CD79 alpha immunoreactivity. The study was performed on cytological samples of 70 canine lymphomas subtyped on the basis of the updated Kiel classification system. Additionally, cytologic samples were examined immunocytochemically for the CD3 and CD79 alpha antigens presence and thus immunophenotype of neoplastic growth was confirmed. The cytopathological and immunocytochemical diagnoses were then compared; in order to measure the concordance between immunocytochemistry (IC) result and Giemsa stain result of the same sample the Cohen's kappa coefficient was calculated. On the basis of the results of immunocytochemistry of 70 cases of canine lymphoma examined 42 were recognized as B cell lymphoma and 28 as T cell lymphoma. Full accordance between the results of routine cytopathology and IC was obtained in 63 out of 70 examined dogs (90% of cases). It can be concluded that cytopathological examination of Giemsa stained smears is helpful in determining the lymphoma cells immunophenotype. Additionally, it seems that combination of routine cytopathology and immunocytochemistry in cases of canine lymphomas allows to obtain the precise diagnosis in 90% of cases, and allows to receive most important information that is necessary for planning of appropriate therapy and to determine prognosis. Finally, this routine procedure allowed to eliminate the need of collection of tissue samples during surgery or core-biopsy and thus time, cost and patient discomfort related to more complex and invasive medical procedures can be easily reduced.

Practical aspects of immunocytochemistry in canine lymphomas

The aim of this study was to evaluate the utility of immunocytochemistry in a standard veterinary practice and to determine the immunophenotype of tumor cells in cases of multicentric lymphoma in dogs by immunocytochemical analysis of fine-needle biopsy specimens. The study was performed on cytological samples collected from 54 dogs, in which multicentric lymphoma was recognised based on clinical data, cytology or cytology and histology, and follow-up information. Diagnosis of lymphoma was established according to the updated Kiel classification. Immunocytochemical assays were conducted using commercially available antibodies to the pan T-lymphocyte marker CD3 and B cell antigen receptor complex CD79 alpha. Among all animals examined B cell lymphoma was recognized in 42/54 (77.8%) of cases, while in the remaining 12/54 (22.2%) of dogs T cell lymphoma was recognized. In 11 animals with lymphoma recognized cytologically, in which an entire lymph node was obtained for histology, the results of routine cytology and immunocytochemistry fully corresponded with findings revealed by histology and immunohistochemistry. Immunocytochemistry can be successfully conducted in smears stored at room temperature for 24 hours without changes of staining results. It can be stated that application of standard cytopathological assessment in connection with immunocytochemistry of lymph nodes samples collected from dogs with lymphoma is a method of choice for establishing final diagnosis, and avoids the need for reexamination or collection of tissue samples for histopathology and immunohistochemistry during surgical procedures in ambiguous cases.