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Analysis of feline dual lymphocyte populations observed by flow cytometry
C Walker1, S Bao, P J Canfield
1Department of Veterinary Pathology, University of Sydney, N.S.W., Australia.
Insights
Feline immunodeficiency virus (FIV) impacts small lymphocytes, altering T-cell proportions. Large lymphocytes remain unaffected, suggesting FIV primarily targets specific lymphocyte subsets in cats.
Area of Science:
- Veterinary Immunology
- Flow Cytometry
- Feline Infectious Diseases
Background:
- Flow cytometric analysis (FCM) commonly reveals two distinct lymphocyte populations in cats: small and large lymphocytes.
- These populations were confirmed by correlating FCM data with peripheral blood film analysis.
- Dual lymphocyte populations are more prevalent in feline immunodeficiency virus-positive (FIV+) cats.
Purpose of the Study:
- To investigate the characteristics and FIV-related differences between small and large lymphocyte populations in cats.
- To determine the impact of FIV on lymphocyte subset distribution within these populations.
- To assess the clinical relevance of analyzing both small and large lymphocytes in feline immunology studies.
Main Methods:
- Flow cytometric analysis (FCM) of feline lymphocyte subsets.
- Correlation of FCM data with peripheral blood film microscopy.
- Analysis of lymphocyte subset proportions (CD4+, CD8+, Pan T+, B cells) in small and large lymphocytes.
- Comparison between FIV-positive (FIV+) and FIV-negative (FIV-) cats, considering health status, age, gender, and breed.
Main Results:
- FIV+ cats showed a higher proportion of large lymphocytes and fewer small lymphocytes compared to FIV- control cats.
- Small lymphocytes contained a greater proportion of CD4+ cells than large lymphocytes, irrespective of FIV status or health.
- FIV+ cats had significantly lower absolute counts of small T cells (CD4+ and CD8+) but similar numbers of small B cells and all subsets of large lymphocytes compared to FIV- cats.
- The proportion of Pan T+ cells was higher in small lymphocytes in FIV- cats, but reversed in FIV+ cats.
- CD8+ cell proportions differed between small and large lymphocytes in healthy FIV- cats but not in sick FIV- or any FIV+ cats.
Conclusions:
- Feline immunodeficiency virus (FIV) appears to predominantly affect small lymphocytes, particularly T-cell subsets, while large lymphocytes remain largely unaffected.
- Significant differences in lymphocyte subset distribution exist between small and large lymphocytes, regardless of FIV status.
- Routine lymphocyte subset analysis in feline disease studies should include both small and large lymphocyte populations for comprehensive results.
Abstract:
Two discrete lymphocyte populations were observed commonly on flow cytometric analysis (FCM) of feline lymphocyte subsets. The identity of these populations as small and large lymphocytes was established by correlating data from FCM with that from peripheral blood films. Dual lymphocyte populations were more likely to be seen in feline immunodeficiency virus-positive (FIV(-)+ ve) cats but their occurrence was not affected by health status, age, gender or breed. FIV(-)+ ve cats had a significantly higher proportion of large lymphocytes than FIV-negative (FIV(-)- ve) cats. However, FIV(-)+ ve cats had significantly fewer small lymphocytes than FIV(-)- ve cats but similar numbers of large lymphocytes. Lymphocyte subset analysis revealed that small lymphocytes had a greater proportion of CD4+ cells than large lymphocytes, regardless of the FIV or health status of the cat. In FIV(-)- ve cats, small lymphocytes had a greater proportion of Pan T + lymphocytes than large lymphocytes, but the converse was seen in FIV(-)+ ve cats. The proportion of CD8 + cells was higher in small lymphocytes than large lymphocytes in well FIV(-)- ve cats but this distinction was not seen in sick FIV(-)- ve cats or FIV(-)+ ve cats of any health status. Regardless of health status, FIV(-)+ ve cats had a lower absolute count of small lymphocytes which were T cells (due to lower numbers of both CD4 + and CD8 + cells) than FIV(-)- ve cats. The numbers of small B cells were similar for both FIV(-)+ ve and FIV(-)- ve cats. However, there were no differences between FIV(-)+ ve and FIV(-)- ve cats in the absolute values of any subset of the large lymphocytes, which suggested that FIV may affect only small lymphocytes. Statistically, the inclusion or exclusion of the large lymphocyte population for routine lymphocyte subset analysis did not affect the overall results. However, because there were significant differences in subset distribution between small and large lymphocytes, analysis of both groups should be included in studies examining the role of lymphocytes in disease.
