Bence-Jones protein is a type of abnormal protein present in the urine of some 35 to 65 per cent of patients with multiple myeloma. This disease, myelomatosis, is characterized by a large increase in the number of plasma cells, which are probably of an abnormal type. Associated with the plasma cell proliferation is a moderate to large increase in the globulin fraction of serum, the total globulin level at times reaching values of 11 to 12 gm./100 ml. Generally, the increased globulin behaves electrophoretically as gamma globulin. On occasions, a peak, the so-called "M" peak, is seen between the beta and gamma globulin fractions, and even more rarely, in the alpha globulin region. Recent studies have shown that gamma globulins are made up of four peptide chains linked together as a unit. The inner two are the longer and are referred to as H (heavy) chains; the outer two are shorter and are called L (light) chains. In myelomatosis, there appears to exist a considerably increased and unbalanced production of the two forms, so that serum contains a high level of abnormal gamma globulins. These may be either the normal type of gamma globulin, designated as 7S or IgG, or the less common IgA type. The excess of short L forms is excreted and is detected in the urine in the form of those abnormal proteins first detected by Bence-Jones some 100 years ago.
Normal proteins, such as the common albumins and globulins, when heated, do not coagulate and precipitate out of solution until the temperature reaches 56 degree to 70 degree. Bence-Jones proteins coagulate at a much lower temperature, 40 degree to 60 degree of Celcius,; furthermore, unlike normal proteins, the precipitated Bence-Jones proteins redissolve as the temperature of the solution is increased to between 85 degree and 100 degree of Celcius., and often reprecipitate as the temperature is again decreased to 45 degree to 50 degree of Celcius. Because of this peculiar behavior on heating, Bence-Jones proteins have been referred to as pyroglobulins. The Bence-Jones proteins have a molecular weight of the order of 45,000, roughly one-fourth that of complete gamma globulin molecules.
Normal proteins, such as the common albumins and globulins, when heated, do not coagulate and precipitate out of solution until the temperature reaches 56 degree to 70 degree. Bence-Jones proteins coagulate at a much lower temperature, 40 degree to 60 degree of Celcius,; furthermore, unlike normal proteins, the precipitated Bence-Jones proteins redissolve as the temperature of the solution is increased to between 85 degree and 100 degree of Celcius., and often reprecipitate as the temperature is again decreased to 45 degree to 50 degree of Celcius. Because of this peculiar behavior on heating, Bence-Jones proteins have been referred to as pyroglobulins. The Bence-Jones proteins have a molecular weight of the order of 45,000, roughly one-fourth that of complete gamma globulin molecules.
Tidak ada komentar:
Posting Komentar