Abstract
Cell-mediated immune mechanisms may contribute to hypersensitivity reactions following ingestion of cow's milk. We assessed in vitro lymphoproliferation to purified cow's milk proteins in sensitized lymphocytes from the spleen, mesenteric lymph nodes and peripheral blood of guinea pigs consuming cow's milk. Blood and lymph node cells were quite responsive but splenocytes responded poorly. Orally sensitized guinea pigs responded best to a-casein, β-casein and β-lactoglobulin and minimally to a-lactalbumin. Even two months after oral exposure, guinea pig mesenteric lymph node lymphocytes still proliferated when cultured with a-casein and β-casein. Refeeding cow's milk to guinea pigs after a milk-free interval following the initial exposure did not boost the proliferative response and may have induced suppression. The effect of nylon wool column enrichment of T cells prior to culture demonstrated the essential role of antigen-presenting cells in T cell activation by cow's milk proteins. Our results suggest the optimum length of time required for oral sensitization to a-casein, β-casein and β-lactoglobulin is 2 weeks. However, prolonged feeding for 4 weeks with cow's milk down-regulated the antigenic response and upregulated the proliferative response to a polyclonal T cell mitogen (ConA). These results suggest that feeding cow's milk can induce antigen specific T cell responses which are both local and systemic. The lymphocyte proliferation assay with highly purified antigens could be useful in elucidating the fundamental cellular mechanisms of cow's milk allergy.