The RH blood group system

A third blood group system was discovered from experiments developed by Landsteiner and Wiener in 1940 with monkey blood of the genus Rhesus. These researchers found that by injecting the blood of this monkey into guinea pigs, antibodies were produced to combat the introduced red blood cells.

Centrifuging the blood from the guinea pigs resulted in serum containing anti-Rh antibodies that could agglutinate the red blood cells of the monkey. Rhesus. The conclusions obtained would lead to the discovery of a membrane antigen that was named Rh (Rhesus), which existed in this species and not in others such as guinea pigs and therefore stimulated the production of antibodies called anti-Rh.

There is at this moment an evolutionary inference: if the proteins that exist in the red blood cells of various animals can resemble it, this may be a sign of evolution. In the human species, for example, we have various types of blood systems that can be observed in other species mainly of higher apes.

Analyzing the blood of many human subjects, Landsteiner found that by mixing the individual's blood droplets with the anti-Rh-containing serum, about 85% of the individuals had agglutination (and belonged to the white race) and 15% did not. It was thus defined "the Rh blood group +(had Rh antigen), and "the Rh group -" (did not have Rh antigen).

In plasma the anti-Rh antibody does not occur naturally, similar to what happens in the Mn system. The antibody, however, can be formed if a person from the Rh group -, receives blood from a person from the Rh group +. This problem with blood transfusions is not as serious unless transfusions occur repeatedly, as is the case with the MN system.

The Rh System Inheritance

Three pairs of genes are involved in Rh factor inheritance, thus dealing with multiple allele cases.

For simplicity, however, we consider the involvement of only one of these pairs in the production of the Rh factor, which is why it is considered a case of simple Mendelian inheritance. The gene R, dominant, determines the presence of Rh factor, while the gene rrecessive conditions the absence of that factor.

Phenotypes Genotypes
Rh + RR or Rr
Rh - rr