CD28 and psychiatric disorder: CD28 is a co-stimulatory molecule on the surface of T cells that provides a second signal for T cell activation by binding to the T cell receptor.[37] CD45RA is a subtype of the CD45 molecule that participates in T cell differentiation.[38] Although there is a lack of relevant literature confirming the association of CD28 or CD45RA with AN, available studies support the association of CD28 and CD45RA with other psychiatric disorders.