How are Type IV hypersensitivity reactions different from all other types (I, II, or III) of hypersentivity reactions?

Hemodialysis is a renal replacement therapy used to remove waste products and excess fluid from the blood when the kidneys are unable to perform this function adequately. The physiological processes involved in hemodialysis include:

A) Solute movement toward a solution with a higher concentration:

While solute movement occurs during hemodialysis, it is typically from a solution with a higher concentration to one with a lower concentration, rather than the opposite. This movement facilitates the removal of waste products and excess solutes from the bloodstream.

B) Water movement toward a solution with a lower solute concentration:

Correct. Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In hemodialysis, water moves out of the bloodstream, across the semipermeable membrane of the dialyzer, and into the dialysate solution, which has a lower solute concentration. This process helps remove excess fluid from the body.

C) Blood cells and protein movement through the semipermeable membrane:

Blood cells and proteins are too large to pass through the pores of the semipermeable membrane in the dialyzer during hemodialysis. Therefore, the primary exchange occurs between smaller molecules such as urea, creatinine, electrolytes, and water.

D) Osmosis of water movement and diffusion of solute movement:

Correct. Hemodialysis involves both osmosis and diffusion. Osmosis refers to the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. Diffusion is the movement of solutes from an area of higher concentration to an area of lower concentration. Together, these processes facilitate the removal of waste products and excess fluid from the bloodstream during hemodialysis.

Chronic osteoarthritis (OA) is a degenerative joint disease characterized by the breakdown of joint cartilage and underlying bone changes. The pathophysiological process of OA involves various factors contributing to joint pain and inflammation. Here's why option C is the correct choice:

A) Inflammation results from deposition of crystals in the synovial space of joints producing irritation:

This statement is more characteristic of crystal-induced arthritis, such as gout or pseudogout, where crystals (e.g., urate or calcium pyrophosphate crystals) deposit in the joints and cause acute inflammation and irritation. While inflammation may occur in OA, it is primarily a result of mechanical stress and cartilage degradation rather than crystal deposition.

B) Inflammation is caused by immune complex and autoantibody deposition in connective tissue:

This statement is more characteristic of autoimmune diseases such as rheumatoid arthritis (RA), where immune complex deposition and autoantibody production lead to chronic inflammation and joint damage. In OA, inflammation is not primarily mediated by immune complex deposition or autoantibodies.

C) Joint inflammation occurs when chondrocyte injury destroys joint cartilage, producing osteophytes:

Correct. In osteoarthritis, joint inflammation occurs as a result of chondrocyte injury and cartilage breakdown. Over time, the degenerative changes in the joint lead to the formation of osteophytes (bone spurs) at the joint margins. These changes can irritate surrounding tissues, including the synovium, ligaments, and tendons, contributing to joint pain and inflammation.

D) Joint destruction happens due to an autoimmune inflammation involving IgG response to an antigen:

This statement is more characteristic of autoimmune arthritis, such as rheumatoid arthritis (RA), where autoantibodies (e.g., rheumatoid factor, anti-citrullinated protein antibodies) target joint tissues, leading to chronic inflammation and joint destruction. In OA, joint destruction primarily results from mechanical stress and wear-and-tear on the joint structures rather than autoimmune mechanisms.