The class I major histocompatibility complex (MHC) presents self-developed peptides to specific T cells to induce cytotoxity against infection. The MHC proteins are encoded by multiple loci that express numerous alleles to preserve the variability of the antigen-presenting ability in each species. The mechanism regulating MHC mRNA and protein expression at each locus is difficult to analyze because of the structural and sequence similarities between alleles. In this study, we examined the correlation between the mRNA and surface protein expression of swine leukocyte antigen (SLA)-1∗0401 after the stimulation of peripheral blood mononuclear cells (PBMCs) by Staphylococcus aureus superantigen toxic shock syndrome toxin-1 (TSST-1). We prepared a monoclonal antibody (mAb) against a domain composed of Y102, L103 and L109 in the α2 domain. The Hp-16.0 haplotype swine possess only SLA-1∗0401, which has the mAb epitope, while other haplotypes possess 0 to 3 SLA classical class I loci with the mAb epitopes. When PBMCs from SLA-1∗0401 homozygous pigs were stimulated, the SLA-1∗0401 mRNA expression level increased until 24 hrs and decreased at 48 hrs. The kinetics of the interferon regulatory transcription factor-1 (IRF-1) mRNA level were similar to those of the SLA-1∗0401 mRNA. However, the surface protein expression level continued to increase until 72 hrs. Similar results were observed in the Hp-10.0 pigs with three mAb epitopes. These results suggest that TSST-1 stimulation induced both mRNA and surface protein expression of class I SLA in the swine PBMCs differentially and that the surface protein level was sustained independently of mRNA regulation.