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A Primer on Immunosenescence and Research in Psoriasis Skin Lesions

Immunosenescence refers to the changes that take place in the immune system during the aging process.  As people age their immune systems deteriorate, our bodies lose their ability to fight infections, and no longer respond to vaccinations.  This field of study is gaining recognition as the average life span is increasing.  Where 150 years ago the average life span was 40 years, it has now dramatically doubled to 80 years.  But have our immune systems progressed with our extended lives?  Older people’s susceptibility to cancer and infection indicates that our immune systems were best equipped for shorter life periods.  Therefore, immunosenescence seeks important questions in empowering people to live healthy and full lives even into their later years.


Some of the age-related changes that cause the onset of immunosenescence have been identified.  Hematopoietic stem cells diminish in their self-renewal capacity, the number of phagocytes decline, cytotoxicity of natural killer cells and the antigen-presenting function of dendritic cells decrease, and there is a decline in humoral immunity.  In addition, there is a decrease in new naïve lymphocytes and the function of memory cell populations, which contributes to the frequency of cancer, inflammatory disorders, and autoimmunity. 


One of the must significant changes is the function of T-cells.  Aging affects every stage of T-cell development, beginning with the involution of the thymus, leading to a reduction in the number of thymocytes and therefore the output of peripheral naïve T-cells.  Eventually, the body has very little virgin T-cells, making it more susceptible to diseases.     


In addition, new research in psoriasis skin lesions explores the role of natural killer cells.  Psoriasis is a chronic inflammatory skin disease.  A recent study evaluated the frequencies of NK cells in blood tissues of psoriasis patients compared to healthy controls.  They found variations, leading to the conclusion that NK cells from this group of psoriasis patients had a less differentiated phenotype. 


Determining the causes of immunosenescence is important in identifying and reconstructing immune dysfunctions.  This will help lead to healthier lives in the aging process and increasing life expectancy. 


Sources: 1, 2, 3


[image by University of Kent]

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