Immunophenotypic characterization and clinical outcome in cats with lymphocytosis

Abstract

Background: Lymphocytosis is relatively common in cats, but few studies describe lymphocyte populations or the clinical course associated with different immunophenotypic expansions.Hypothesis/Objectives: We hypothesized that cats frequently develop nonneoplastic lymphocytosis and that different neoplastic immunophenotypes have variable prognoses. We aimed to characterize the lymphocyte expansions in a large population of cats with lymphocytosis and to assess clinical presentation and outcome in a subset.Animals: Three cohorts of cats older than 1 year with lymphocytosis (>6000/μL) were examined to define immunophenotypic categories (n = 146), evaluate outcome (n = 94), and determine prevalence of immunophenotypes (n = 350).Methods: Retrospective study of cats with blood submitted for flow cytometry.Medical records (n = 94) were reviewed for clinical data, treatment, and survival information. Results: Five major immunophenotypic categories were identified: B cell, heterogeneous (≥2 lineages expanded), CD4+ T cell, CD4−CD8− (double negative [DN]) T cell, and CD5-low-expressing T cell. B-cell and heterogeneous phenotypes were more consistent with a non-neoplastic process, having polyclonal antigen receptor gene rearrangements, younger age at presentation, lower lymphocyte counts, and prolonged survival. The neoplastic phenotypes, CD4+ T cell, DN T cell, and CD5 low T cell, had different median survival times (752 days [n = 37], 271 days [n = 7], 27.5 days [n = 12], respectively). Among CD4+ T-cell cases, cats with abdominal lymphadenopathy, intestinal involvement, or both and females had shorter survival. Among 350 cats with lymphocytosis, CD4+ T-cell lymphocytosis was most common, followed by heterogeneous and B-cell phenotypes. Conclusions and Clinical Importance: Neoplastic CD4+ T-cell lymphocytosis is common in cats and has a prolonged clinical course compared to aberrant T-cell

Composition of lymphocyte subpopulations in normal and mildly reactive peripheral lymph nodes in cats

“…27 In 2020, Rout et al described a proportion of CD4 -CD8cells of 22.6% in the peripheral blood of cats when investigating feline lymphocytosis. 13 This doublenegative cell type represented 57.90% ± 11.95% in normal feline LNs in the present cohort. Comparability between data from the present study and that of Rout et al 13 is limited because different marker combinations prohibit an identical gating strategy allowing the separation of CD4 -CD8 -B cells and other subpopulations.…”

“…13 This doublenegative cell type represented 57.90% ± 11.95% in normal feline LNs in the present cohort. Comparability between data from the present study and that of Rout et al 13 is limited because different marker combinations prohibit an identical gating strategy allowing the separation of CD4 -CD8 -B cells and other subpopulations. Further characterisation of this population is required.…”

“…All LNs from an individual cat were then trimmed clean of surrounding fat and connective tissue and were cut in half. Tissue Table 1 Comparison of published data for different labelling patterns with different clones from monoclonal antibodies directed against feline leukocytes in feline whole blood [10][11][12][13] Antibody Clone…”

“…Previous studies have investigated restricted flow cytometric (FCM) antibody panel data for feline whole blood/ peripheral blood mononuclear cell samples. [10][11][12][13] They demonstrated data for clones of monoclonal antibodies (mAbs) against CD4, CD5, CD8, CD21 and CD56 (Table 1). No reference data for feline LNs using these antibodies currently exist.…”

Novel Multicentric Hepatic Lymphoma with Extrahepatic Biliary Obstruction Associated with Duodenal Perforation in a Cat

“…A sample of hepatic tissue was aspirated into liquid media (90% normal saline, 10% feline serum) and processed for flow cytometry using routine methods, as previously described [ 29 ]. Cells were stained with a single panel of antibodies recognizing canine CD21 (clone CA2.1D6), canine CD18 (clone CA1.4E9), and feline CD5 (clone FE1.1B11), CD4 (clone vpg34), and CD8 (clone vpg9).…”