Correlation of lymphocyte proliferating cell nuclear antigen expression with dietary cow's milk antigen load in infants with allergy to cow's milk

Background: Controversial results have been reported on the participation a nd diagnostic value of lymphocyte reactivity in cow's milk (CM) allergy. In this study, we used a specific nuclear marker to evaluate lymphocyte proli feration in IgE-mediated CM allergy in infants, and examine its relation wi th diets containing different CM antigen loads. Methods: Infants with IgE-m ediated CM allergy, as assessed by open provocation and RAST, were grouped according to their exclusive diet, either CM formulae, breast feeding, or h ydrolysed whey formulae. A group of non-atopic infants receiving CM was als o examined. Lymphocyte proliferation to B-lactoglobulin was evaluated by qu antitation of the proliferating cell nuclear antigen (PCNA) expression in p eripheral blood mononuclear cells, by flow cytometry. Immunophenotypic surf ace markers were also examined. Results: A marked difference of PCNA expres sion between CM-fed allergic infants and healthy controls was observed (p<0 .001). In this setting, PCNA expression greater than or equal to 10% was hi ghly specific and sensitive as a marker of CM allergy in CM-fed infants. Mo reover, a significant correlation (p<0.001) between antigen load and PCNA w as established in CM-allergic infants under different diets, higher values obtained with increasing antigen loads. In addition, within the group fed h ydrolyzed formulae, low-molecular-weight products resulted in marginally lo wer PCNA expression than higher-molecular-weight formulae. No differences i n immunophenotype were found, with the exception of a higher CD23 expressio n in the breast-fed group. Conclusions: PCNA could be a useful marker in th e assessment of lymphocyte proliferation to CM antigens. Low CM antigen die ts are related with reduced lymphocyte reactivity, which may partly explain the clinical benefit observed with such diets.