CD4 and lymphopenia: Lessons from drug-related TDL, immunopathology studies of biopsied lesions and clinical cases reports indicate different cellular and humoral mechanisms implicated in the pathogenesis; lymphopenia-induced lymphoproliferation, persistent selected peripheral lymphopenia (CD8 or CD4 T cells), exaggerated innate immunity response either with pathogenic potential or regulatory / compensatory potential and exaggerated B cells response (16, 99).