To study the anti-allergy effects of probiotic Lactobacillus acidophilus L-92 (L-92), changes in the immunomodulatory effect and key cell components in response to media pH in which L-92 cells were cultivated were studied using microarray and proteome analyses. Growth of L-92 cells was restricted if the medium pH was uncontrolled and the release of IL-12 from splenocytes increased as the pH decreased during cell growth. The decrease in pH from 5.0 to 4.5 at the exponential phase of growth had the greatest effect on the release of IL-12. When L-92 cells were cultured at low pH, the release of IL-12, IFN-gamma and IL-10 was increased but IL-4 release was decreased from splenocytes. Comparative transcriptome analysis between L-92 cells cultured at pH 5.0 and pH 4.5 in MRS medium revealed significant up-regulation of 121 genes and down-regulation of 92 genes. Among the significantly changed genes, heat shock proteins such as GroES and GroEL were considered to be the most likely components affecting immunomodulation. Proteome analysis of the cell wall-associated components of L-92 also supported increases in GroES and GroEL as cell surface components in L-92 cells cultured at a lower pH. In conclusion, increases in cell wall-associated components of L-92, such as GroES and GroEL, in response to a pH decrease affect the release of certain cytokines from splenocytes. (C) 2012, The Society for Biotechnology, Japan. All rights reserved.