What physiological process includes swelling due to fluid accumulation in tissue?

The physiological process that includes swelling due to fluid accumulation in tissue is inflammation. Inflammation is a complex biological response of the body's tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. One of the hallmark signs of inflammation is swelling, also known as edema, which occurs as a result of increased blood flow to the affected area and increased permeability of blood vessels. This allows not just plasma but also various proteins and immune cells to escape into the surrounding tissue, leading to the accumulation of fluid.

The process is beneficial as it helps to isolate pathogens, contain infections, and initiate tissue repair. The other options pertain to different phenomena: immunosuppression relates to a reduced immune response, incompatibility often refers to an adverse reaction in transfusions or organ transplants, and infection specifically involves the invasion of the body by pathogenic microorganisms. While infection can lead to inflammation, it is inflammation that directly describes the physiological process resulting in swelling.