[The immune system, atherosclerosis and persisting infection]

Area of Science:

• Immunology
• Pathology
• Cardiovascular Science

Background:

• Atherosclerosis is a chronic inflammatory disease driven by low-density lipoprotein (LDL).
• The early immune response to LDL and its role in atherogenesis are not fully understood.
• The involvement of regional lymph nodes in the immune response to atherosclerosis requires further investigation.

Purpose of the Study:

• To identify the source of immune and inflammatory responses to LDL in atherosclerosis.
• To investigate the role of lymph nodes in the early stages of T-cell-mediated immunity in atherosclerosis.
• To examine the correlation between cellular changes in lymph nodes and the severity of atherosclerotic lesions.

Main Methods:

• Analysis of immune cell populations in lymph nodes draining affected arterial regions.
• Correlation of lymph node cellular changes with histological assessment of atherosclerotic lesions.
• Investigation of immune responses in the presence of *Chlamydia pneumoniae* infection.

Main Results:

• Lymph nodes near major blood vessels are the primary site of immune response to LDL.
• Early T-cell activation, including CD4+ T-lymphocytes, mononuclear cells, and B-lymphocytes, occurs in these lymph nodes.
• Cellular changes in lymph nodes correlate with atherosclerotic lesion severity and reflect immune inflammation in fatty streaks and plaques.
• A paradoxical immunosuppression was observed in cases with *Chlamydia pneumoniae*, characterized by suppressed mononuclear and T-lymphocyte function.

Conclusions:

• Regional lymph nodes are critical in initiating the immune response to LDL in early atherosclerosis.
• Cellular changes in lymph nodes serve as indicators of atherosclerotic lesion progression.
• *Chlamydia pneumoniae* may exert immunosuppressive effects, hindering the immune response in atherosclerosis.