Thymus

The thymus is the primary site of T-cell maturation. Naive T-cells travel from bone marrow to the thymus, where they undergo positive and negative selection - learning to recognise self from non-self. Without this process, the immune system cannot mount targeted responses.

The thymus secretes a family of peptide hormones - thymosin α1, thymosin β4, thymulin, and thymopoietin - that coordinate T-cell development within the gland and continue to signal outside it. Thymic peptide levels decline with age.

What makes bovine thymus scientifically interesting is the near-identical amino acid sequence of these peptides between cattle and humans. Thymosin β4 is 100% conserved across species - the same 43-amino-acid peptide, with no substitutions.