Background Bovine casein leads to an expansion of lymphocytes expressing the cutaneous lymphocyte antigen and to specific lymphocyte proliferation in a subgroup of patients with milk-responsive atopic dermatitis (AD). The casein fraction is composed of different proteins with defined and completely different sequences.
Objective To define the stimulatory capacity of the major casein protein (α and k) in lymphocyte proliferation assays with cells from milk-allergic and non-allergic individuals.
Methods Proliferative responses of peripheral blood mononuclear cells to lipopolysaccharide-depleted casein subfractions were measured by thymidine incorporation. Lymphocytes from milk-responsive patients with AD were compared with cells from non-responsive patients with AD and to non-atopic individuals, Atopic individuals with immediate symptoms following consumption of cow's milk were included as positive controls. Casein-specific T-cell clones (TCC) from four patients with milk-responsive AD were restimulated with unfractioned casein and K-casein.
Results Higher proliferative responses to unfractionated casein and α-,β and casein were observed in milk-responsive patients compared with non-responders. Unfractionated casein and K-casein discriminated best between the milk-responsive patients with AD and non-responders. Twenty-five of 31 TCC from patients with milkresponsive AD reacted to the mixed casein preparation and K-casein.