No Quantitative Relationship between CR1 and Lutheran Expression on Erythrocytes: In(Lu) Gene Product Is Not a Common Regulator of CR1 Expression on Erythrocytes

Abstract

The density of CR1, the C3b/C4b receptor (CD35), on erythrocytes (E) (CR1/E) is genetically determined. However, the broad distribution of CR1/E within a given genotype suggests that other genetic elements might contribute to the regulation of CR1/E. In some pathological conditions, including systemic lupus erythematosus (SLE), AIDS and hemolytic anemia, CR1 deficiency parallels the severity of the disease. When compared to healthy individuals, an accelerated decrease in CR1/E in these patients has been demonstrated, but other mechanisms interfering with CR1 density regulation during erythropoiesis might also contribute. In exceptional circumstances, CR1/E can be dramatically decreased in healthy individuals by the effect of a regulatory gene, In(Lu), that switches off various surface molecules on E, the structure genes of which are located on four different chromosomes, suggesting a transcription regulatory role for In(Lu) gene products. The hypothesis that products of this gene could physiologically regulate the surface density of all these molecules has been tested by determining Lu^b density on E (Lu^b/E) using quantitative flow cytometry. Lu^b antigenic sites were then compared to CR1/E among healthy individuals of the different CR1 density phenotypes, SLE patients with and without CR1 deficiency, and an exceptional SLE patient totally lacking CR1/E and reticulocytes. No quantitative relationship was found between CR1 and Lu^b expression in either normal or pathological conditions. These data establish that In(Lu) products are not involved in normal or pathological CR1 density regulation.

Complement receptor 1 red cell expression is not controlled by the In(Lu) gene

“…They suggested that other CR1 mutations might be important in determining copy number. Finally, in a French study of both CR1 and Lutheran system antigens, there was no weakening of Lutheran system antigens in donors with weak CR1 23 …”

Understanding the Knops Blood Group and its Role in Malaria

“…Moulds, unpublished data). Although it was initially reported that ln(Lu) could suppress expression of the Knops antigens 20 , however, later studies indicated that CR1 expression was not controlled by this gene 21–22 …”