Introduction: Flow cytometry (FC) is widely used in humans and dogs to
diagnose and characterize hematopoietic neoplasms. Conversely, its use in
feline patients is still limited, leading to a lack of standardized protocols and
subjective data interpretation.
Methods: Herein, we describe FC features of circulating lymphoid subsets in a
total of 20 cats: 9 healthy cats, 6 diseased cats without hematopoietic neoplasm,
and 5 cats with probable chronic lymphocytic leukemia (CLL), using a panel of
10 antibodies and a multicolor approach, in terms of both cell size (nFSC) and
degree of antigen expression (MFI).
Results: Three main subsets were identified in healthy cats and diseased cats
without hematopoietic neoplasm (namely, CD5 + CD45R-, CD21 + CD45R +
and CD5 + CD45R+). CD4 + CD8- cells outnumbered CD4- CD8 + cells. Low
percentages of CD4 + CD8 + and CD134 + cells were also present. MHCII had
higher fluorescence intensity in B- than in T-cells. CD9 was not expressed on
leukocytes surface, but on small events possibly referable to platelet clumps. In
diseased cats without hematopoietic neoplasm, each T-cell subset was larger in
size than in healthy cats. Finally, in cats with probable CLL the leading phenotype
was CD5 + CD45R-CD4 + CD8-CD134 + MHCII+ and cell size overlapped with
the one of the other diseased cats.
Discussion: Our results are expected to lay the ground for a more standardized
approach to feline samples for FC, and a more objective data interpretation,
ultimately leading to improved diagnostic accuracy. Further studies are needed
to assess the biological, diagnostic and prognostic value of specific FC patterns
in feline medicine
