Regarding the effect of ATRA on the increased levels of TNF-α, we suggest a positive effect on the Th1 response of dogs with leishmaniasis, in contrast to the results obtained in vitro in mouse PBMC, in which the supplementation with ATRA reduced the TNF-α mRNA, a difference that may be related to the different host and experimental designs used in the studies. Here, TNF is linked to leishmaniasis.