Changes in cell surface markers and cytokine transcription were analyzed in lamina propria lymphocytes from control animals (noninfected calves) and calves after a single high but nonprotective primary infection with Ostertagia ostertagi. Flow cytometry of cells recovered from the lamina propria showed an increase in the percentages of IgM+, WC1+, and IL-2R+-bearing cells 10 days after infection; however, 2 mo after infection, cell staining was comparable to preinfection levels. Transcription levels of interleukins IL-2, IL-4, IL-10, and interferon (IFN)-gamma mRNA were measured using a competitive reverse transcription-polymerase chain reaction. Results indicated elevated levels of IL-4 and IFN-gamma in the infected animals at 10 days and at 60 days after infection. Transcription of IL-10 also increased; however, this change was not observed until 60 days postinfection.