In order to examine the relation of known intestinal lesions to changes in T-cell phenotypes and integrin expression, 16 male 10-day-old Holstein calves were divided into two groups. For 28 days of the experiment, eight males were fed NutriMilk in which 50% of the crude protein was soya protein, and eight control animals, with NutriMilk containing only milk casein. The animals fed soya protein showed shorter jejunal villi with a corrugated surface and deeper crypts compared with the control calves. A higher density of CD8+ cells in the intestinal mucosa and a decrease of these cells in peripheral blood were found in calves fed soya protein. The number of CD11b-positive cells was decreased in the peripheral blood of calves fed soya protein. Lower expression of integrin could be related to the appearance of non-mature polymorphonuclear cells. It is not clear if the decrease in CD11b expression on blood cells could also be influenced by milk replacer, i.e. soya protein.