Introduction

In human lymphomas, it has been shown that the macrophages present in the tumor have an influence on their behavior; however, studies on this topic are scarce in veterinary medicine. The aim of this work was to determine the relationship between the macrophage infiltrates with the histological grade and the immunophenotype in clinical cases of canine lymphoma.

Methods

Samples from lymph nodes of dogs with lymphoma (n=25) were stained with hematoxylin and eosin to establish the histological grade. Immunohistochemistry was used to determine the tumor immunophenotype (CD3 and CD20 antibodies) and macrophage characterization (Iba1, CD163, iNOS and MAC387 antibodies). Macrophage counting was performed in ten high power fields per sample. Generalized linear models with Poisson distribution were used for statistical analysis.

Results

High grade and B lymphomas showed a higher number of macrophages than their counterparts. A significantly (p<0.001) higher number of macrophages (Iba1+) was detected in high grade (255.86±104.80) and B cell lymphomas (233.18±87.46). The highest numbers of M1 (iNOS+) and M2 (CD163+) macrophages were observed in B cell lymphomas. High grade lymphomas showed a higher (p<0.001) number of CD163+ cells (182.86±79.79 vs. 113.00±98.88) and recently recruited MAC387+ macrophages, that were the most abundant in T (107.15±49.55) than in B (104.67±38.26) lymphomas.

Conclusion

The number and type of macrophages present in canine lymphoma is related to the immunophenotype and the grade. In those with high grade, macrophages are actively recruited and show a predominant M2 phenotype, that has been associated with a protumoral activity.

Funding Information

None.