Immunosenescence refers to the gradual decline in the immune system's function as individuals age. This process affects various immune cells, leading to a reduced ability to respond to infections and vaccines. As a result, older adults may experience increased susceptibility to diseases and a slower recovery from illnesses. Factors contributing to immunosenescence include chronic inflammation, reduced production of thymus hormones, and changes in T cells and B cells. These changes can impair the body's ability to recognize and fight off pathogens, making it essential to understand and address the implications of immunosenescence in aging populations.