There is an ongoing discussion about cow’s milk and its variants primarily focusing on the A1 variant in contrast to the A2 variant and their health-related impacts. The difference between these variants lies in a single amino acid alteration at position 67 of β-casein. This alteration is presumed to make the A1 variant more susceptible to enzymatic breakdown during milk digestion, leading to an increased release of the peptide β-casomorphin-7 (BCM-7), which is discussed to be associated with various health risks. Thus, we analyzed the influence of A1 and A2 milk on Concanavalin A (ConA)-stimulated human peripheral blood mononuclear cells (PBMCs) in earlier studies. Thereby we were able to show that milk fundamentally inhibits PBMC proliferation, independent of the β-casein variant (Gard, Flad et al. 2024). This points to an anti-proliferative effect of cow´s milk on human PBMCs, regardless of the A1 or A2 β-casein variant. In the recent study, we divided milk of both ß-casein variants in a high molecular weight (>100 kDa) and a low molecular weight (<100 kDa) protein fraction, in order to narrow down the range for the causative factor of this anti-proliferative effect triggered by the milk. The data presented here are highly relevant for human medicine and dairy industry. REFERENCE: Gard, F., L. M. Flad, T. Weisser, H. Ammer and C. A. Deeg (2024). "Effects of A1 Milk, A2 Milk and the Opioid-like Peptide beta-Casomorphin-7 on the Proliferation of Human Peripheral Blood Mononuclear Cells." Biomolecules 14(6).