During infection, innate or acquired immunity is activated. Immunocytes then play a key role in the innate and adaptive immune responses. Immunocyte number and variation reflect the immunity or infection status (Demissie et al., 2013; Hunt et al., 2015). Furthermore, the immunocyte induction of cytokine and antibody production participates in immune regulation and the inflammatory response (Baehner, 1975; Cassatella, 1999). One signaling pathway that promotes the expression of pro-inflammatory genes is the TLR- and MyD88-dependent pathways (Zughaier et al., 2005). In the current study, the L. plantarum G83 strain did not significantly alter the leukocyte amount and variation in the mouse peripheral blood among the groups at different time points. Besides the granulocyte, the amount of leukocytes, lymphocytes, and intermediate cells decreased at 24 h after ETEC inoculation. This effect may have been caused by the high expression of IL-8 and MCP-1, which take part in the immunocytes migration to the site of infection in the intestine. Such results were similar to those of previous reports (Zhu et al., 2014). Lactobacillus supplementation enhanced serum IgG, IgM, and IgA levels and indicated that probiotics could stimulate systemic or mucosal antibody response (Frece et al., 2006; Mizumachi et al., 2009). In the present study, the L. plantarum G83 obviously increased the IgA, IgM, and IgG levels before or after ETEC challenge. IgA has an important role in the protection of mucosal surfaces against pathogens (Galdeano and Perdigon, 2004). The secretory IgA of intestinal mucosa will be detected in next study. Low and intermediate doses of the strain also decreased the mRNA levels of IL-1β, −6, and −8 in the jejunum, probably by modifying the immunocyte profile. Early studies confirmed that lactobacilli lower serum IL-6 concentrations after acute ETEC challenge in piglets (Zhang et al., 2010). The aforementioned observations suggested that inflammation was ameliorated in the LDLP and MDLP groups and were consistent with those of previous studies where probiotics exerted dose-dependent effects (Mileti et al., 2009). Lee et al. (2012) found that high-dose L. plantarum CJLP243 (108–1010 cfu kg−1) most substantially improved the growth and health performance of weaning pigs, especially those with bacterium-induced acute bowel inflammation. A recent trial of piglets challenged with F4+ ETEC demonstrated that administering LGG (1012 cfu day−1) failed to prevent F4+ ETEC infection. This failure was probably due to the disruption of microbial and inflammatory responses by excessive probiotic levels (Li et al., 2012). Same probiotic in different doses have different modulation effect on T-cell immune response and mucosal IgA response (Wen et al., 2012, 2015). Thus, only intermediate- and low-dose L. plantarum G83 positively affects acute inflammatory bowel disease.