The prevalence of celiac disease (CD) has increased worldwide, which could be related to some dietary proteins in infant regimens and/or new food processes, affecting CD-predisposed infants and older children or adults differentially. IgA reactivity to human and bovine caseins, as well as yogurt caseins and prolamins from wheat or maize breads, microbial transglutaminase (mTG)-treated or not, was evaluated in three patient groups: G1, <2 years old; G2, approximately 3 years old; and G3 >8 years old. Human caseins were not recognized by IgA, whereas IgA reactivity of G2 and G3 was higher to bovine milk caseins. Immunoreactivity of G1 to yogurt caseins was lower and comparable to controls, with no effects due to mTG treatment. However, mTG treatment increased reactivity of G3 to wheat and maize prolamins. IgA immunoreactivity of CD patients to caseins and mTG-treated or not prolamins was age-dependent, which could reflect a differential manifestation of the effects of such proteins on the intestinal barrier.