Over four years have passed since the first SARS-CoV-2 outbreak, and scientific advancements have reshaped our understanding of immunity and virus dynamics.

As we age, our innate and adaptive immune system undergoes various changes, typically characterized by decreased lymphopoiesis and adaptive immunity, and increased inflammation and myeloid pathologies. Immunosenescence (the gradual deterioration of the immune system associated with ageing), makes individuals more susceptible to infections, less responsive to vaccines, and prone to the development of chronic inflammatory conditions and autoimmune diseases.

自己抗体（ナチュラル自己抗体とも呼ばれる）は、細菌やウイルスなどの外来因子ではなく、体内の自身のタンパク質を標的とする抗体です。健康な個体では、自己抗体の多くはIgMであり、変異のないV(D)J遺伝子によってコードされており、自己抗原に対して中程度の親和性と高いアビディティ（結合力）を示します。