free κ/λ or λ/κ light chain ratio) less than 100, providing that the higher light chain concentration is >100 milligram/liter; and e) a circulating blood plasma cell absolute count of <2x109 and/or <20% of total circulating nucleated cells. Presence of any one of the latter findings indicates that the plasma cell dyscrasia has progressed beyond the MGUS stage.Non-IgM MGUS is a relatively stable condition afflicting 3% of people aged 50 and 5% of people aged 70; on average, it progresses to multiple myeloma at a rate of 0.5-1% cases per year, as defined in studies following patients over a 25-year period. A study conducted by the Mayo Clinic found that MGUS associated with non-IgG myeloma proteins or with serum myeloma protein levels greater than 15 gram/liter had a greater risk per year of progression to multiple myeloma. A Spanish study group found that MGUS patients demonstrating aneuploidy (i.e. abnormal number of chromosomes) in bone marrow cells or >95% of resident bone marrow plasma cells that are clonal in nature also have a greater risk per year of progression to myeloma. In a more recent study, MGUS patients that had the presence of none, 1, 2, or 3 of the three following risk factors, serum M protein levels >15 gram/liter, a non-IgG isotype, and abnormal free light chain ratios, had 5, 32, 37, and 58% chances, respectively, of progressing to multiple myeloma within 20 years.
The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. For human blood transfusions, it is the most important of the 43 different blood type (or group) classification systems currently recognized by the International Society of Blood Transfusions (ISBT) as of June 2021. A mismatch (very rare in modern medicine) in this, or any other serotype, can cause a potentially fatal adverse reaction after a transfusion, or an unwanted immune response to an organ transplant. The associated anti-A and anti-B antibodies are usually IgM antibodies, produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses. The ABO blood types were discovered by Karl Landsteiner in 1901; he received the Nobel Prize in Physiology or Medicine in 1930 for this discovery. ABO blood types are also present in other primates such as apes and Old World monkeys. History
Discovery
The ABO blood types were first discovered by an Austrian physician, Karl Landsteiner, working at the Pathological-Anatomical Institute of the University of Vienna (now Medical University of Vienna). In 1900, he found that red blood cells would clump together (agglutinate) when mixed in test tubes with sera from different persons, and that some human blood also agglutinated with animal blood. He wrote a two-sentence footnote:

The serum of healthy human beings not only agglutinates animal red cells, but also often those of human origin, from other individuals.