ALOX15 and obesity due to melanocortin 4 receptor deficiency: Because macrophage is a major cellular player in metabolic reprogramming and represent an important target of fatty acid metabolites in metabolic disorder [60, 61], the results from current study called attention to further investigation of the S1P-ALOX15 signals in macrophages, not only for understanding obesity-lymphomagenesis but also for finding the potential strategy of immune checkpoint blockade therapy.