In the present study, the expression of two non-receptor protein tyrosine phosphatases in pig spleen lymphocytes (splenocytes) was analyzed. The mRNA-transcripts of PTP1B and Tc-PTP were analyzed by reverse transcriptase-PCR in cultured splenic lymphocytes exposed to different biochemical treatments. Mitogenic stimulation by concanavalin A produced a clear increase in the mRNA relative amounts of both PTPs, after 24-h exposure in primary cultures, and LPS exerted a marked increase of both splice variants of the Tc-PTP (ER and nuclear). Interestingly, both PTPs seem to respond to the redox status, given that the Tc-PTP-mRNA showed a marked increase in the presence of 1.9 mM H₂O₂, and PTP1B showed a similar effect after exposure of the cultured splenocytes to 10 mM N-acetylcysteine for 24 h. Other biochemical treatments of the cultured splenocytes also showed an opposite effect in the mRNA-levels of these PTPs: lowering of the Tc-PTP-mRNA and increase of the PTP1B transcript after exposure to IL-4 and γIFN. The results suggest non-redundant functions of both PTPs, despite their similar structures. The Tc-PTP showed an increase in the mRNA level after H₂O₂ treatment of the splenic lymphocytes for a short time (1.5 h). The results suggest that the intracellular redox status may play an important role in the regulation of the expression of PTP1B and Tc-PTP in splenocytes.