CD28 and asthma: Mediate MR indicated −9.81% (−1.2%, −18.4%) of the effect of CD24 on IgD+ CD38br on asthma is mediated by S‐methylcysteine sulfoxide levels, with a mediated effect value (p = 0.006) is 0.003 (0.0004, 0.006); 21.4% (6.2%, −36.6%) of the effect of CD3 on CD28+ CD4+ on asthma is mediated by 1‐myristoyl‐2‐arachidonoyl‐GPC (14:0/20:4) levels, with a mediated effect value (p = 0.025) is 0.004 (0.001, 0.007).