CD244 and thrombotic thrombocytopenic purpura: Although no correlation was observed between plasma ADAMTS13 activity levels in these remission samples and the number of acute TTP episodes a patient had previously experienced, positive correlations were found between expression of five of the immune genes (KLRB1/CD161 (r = 0.3541), CD244 (r = 0.4909), CD52 (r = 0.3538), MAF (r = 0.4904), HOPX (r = 0.3525) and number of episodes (Fig. 5).