The method described is sensitive and can be used routinely for the quantitative determination of specific IgG anti-D and IgG subclasses in sera.

*Rha and Rhag are MGI nomenclature. SummaryMouse Rhd* and Rhag* genes were targeted using insertional vectors; the resulting knockout mice, and double-knockout descendants, were analysed. Rhag glycoprotein deficiency entailed defective assembly of the erythroid Rh complex with complete loss of Rh and intercellular adhesion molecule 4 (ICAM-4), but not CD47, expression. Absence of the Rh protein induced a loss of ICAM-4, and only a moderate reduction of Rhag expression. Double knockout phenotype was similar to that of Rhag targeted mice. Rhd and Rhag deficient mice exhibited neither the equivalent of human Rh null haemolytic anaemia nor any clinical or cellular abnormalities. Rhd)/) and Rhag)/) erythrocytes showed decreased basal adhesion to an endothelial cell line resulting from defective ICAM-4 membrane expression. There was no difference in recovery from phenylhydrazine-induced haematopoietic stress for double knockout mice as compared to controls, suggesting that ICAM-4 might be dispensable during stress erythropoiesis. Ammonia and methylammonia transport in erythrocytes was severely impaired in Rhag)/) but only slightly in Rhd)/) animals that significantly expressed Rhag, supporting the view that RhAG and Rhag, but not Rh, may act as ammonium transporters in human and mouse erythrocytes. These knockout mice should prove useful for further dissecting the physiological roles of Rh and Rhag proteins in the red cell membrane.

A cohort of 341 symptomless anti-human immunodeficiency virus (HIV)-1 positive individuals was screened over a 6-year period to detect a serum monoclonal gammopathy (MG) and to approach the prognostic significance of such anomaly in HIV infection. Eleven individuals with a MG were followed-up over a mean period of 50 months from the date of discovery of the MG. At the end of this period, the MG had disappeared in seven individuals, was still present in the four others. The appearance of a second MG was noticed in two cases, and of a third in one case. Immunoglobulin (Ig) typing identified eleven IgG kappa and three IgG lambda. Mean serum concentration of MG of individuals with persistent MG (14.3 g/l) and of individuals without (4.2 g/l) was significantly different (P < 0.05). The discovery of a MG was without prognosis value on the disease progression and did not appear as a primary event in the subsequent development of lymphoma.

The proportion of IgG3 anti-D relative to the total anti-D IgG on infants' RBCs is only one- third of the proportion present in maternal serum. The study of the correlations between the amount of IgG1 anti-D and IgG3 anti-D and the severity of HDN suggests that IgG1 anti-D are more important than IgG3 anti-D in the pathogenesis of fetal anemia.