plasmaproteiinit

Plasmaproteiinit, or plasma proteins, are a group of soluble proteins that circulate in blood plasma. They constitute about 7–8% of plasma by weight, and the typical total plasma protein concentration is 60–80 g/L. Most plasma proteins are synthesized in the liver, with notable exceptions including immunoglobulins, which are produced by plasma cells in lymphoid tissue and bone marrow.

Albumins are the largest single class, accounting for roughly 60% of plasma proteins. They maintain colloid osmotic pressure, act as carriers for fatty acids, steroid hormones, and various drugs, and help stabilize blood volume. Globulins are divided into alpha, beta, and gamma fractions. Alpha and beta globulins include transport and enzymatic proteins such as transferrin and apolipoproteins, as well as components of the complement system. Gamma globulins are mainly immunoglobulins produced by plasma cells and provide specific immune defense. Fibrinogen, a smaller fraction, is a crucial coagulation factor that is converted to fibrin during clot formation.

Clinical assessment uses measurements of total protein, albumin, and globulin, often by electrophoresis. The albumin-to-globulin ratio is a useful diagnostic parameter. Abnormal levels can reflect liver disease (hypoalbuminemia), kidney disease (loss of albumin in nephrotic syndrome), malnutrition, or inflammatory and immune conditions (elevated gamma globulins or fibrinogen). Inflammatory states raise certain acute-phase proteins, including fibrinogen. Monoclonal gammopathies, such as multiple myeloma, can cause sharp increases in a single gamma-globulin fraction.