Circulatory CD4-Positive T-Lymphocyte Imbalance Mediated by Homocysteine-Induced AIM2 and NLRP1 Inflammasome Upregulation and Activation Is Associated with Human Abdominal Aortic Aneurysm

<b><i>Introduction:</i></b> CD4-positive T lymphocytes (CD4 cells) play a significant role in human abdominal aortic aneurysm (AAA). However, we know little about the role of the different CD4 subtypes. <b><i>Objective:</i></b> We aimed to discover the circulatory CD4 phenotypic marker profile and the roles of the newly found T helper cell 9 (Th9) and follicular helper T cells (Tfh) and that of inflammasomes in CD4 cells from AAA patients. <b><i>Methods:</i></b> We extracted CD4 cells from 30 AAA patients and 21 age-matched controls. Phenotype-specific transcription factors (TFs) and inflammasomes were analyzed with qRT-PCR. <b><i>Results:</i></b> Th17-, Th1-, Th9-, and Tfh-specific TFs and inflammasome components <i>NLRP1</i> (NLR family pyrin domain-containing 1), <i>NLRP3</i>, <i>NLRC4</i>, <i>AIM2</i> (absent in melanoma 2), <i>PYCARD</i> (apoptosis speck-like protein containing a CARD), and <i>CASP1</i> (caspase 1) were upregulated, and T regulatory cell- and Th2-specific TFs were downregulated in the patients’ peripheral blood CD4 cells. Homocysteine was involved in Tfh and Th17 imbalance by <i>AIM2</i> and <i>NLRP1</i> inflammasome upregulation. Blood total cholesterol level correlated positively with <i>NLRP1</i> expression, and blood low-density lipoprotein level correlated negatively with <i>FOXP3</i> expression. <b><i>Conclusions:</i></b> Inflammasome-induced CD4 cell imbalance was involved in AAA. We thought that AAA might be a consequence of synergism between systemic immune imbalance and local autoimmunity.