Genetic variation in Arizona Mexican Americans: estimation and interpretation of admixture proportions.

Mexican Americans are a numerous and fast growing ethnic population in the United States. Yet little is known about their genetic structure. Since they are a hybrid, it is of interest to identify their parental populations and to estimate the relative contributions of these groups. This information is relevant to historical, biomedical, and evolutionary concerns. New genetic typings on 730 Arizona Mexican Americans for the HLA-A, HLA-B, ABO, Rh, MNSs, Duffy, Kidd, and Kell loci are presented here and they are used to estimate ancestral contributions. We considered both a dihybrid model with Amerindians and Spaniards as proposed ancestors, and a trihybrid model with Amerindians, Spaniards, and Africans as proposed ancestors. A modified weighted least squares method that allows for linkage disequilibrium was used to estimate ancestral contributions for each model. The following admixture estimates were obtained: Amerindian, 0.29 +/- 0.04; Spaniard, 0.68 +/- 0.05; and African, 0.03 +/- 0.02. The interpretation of these results with respect to Amerindian and Spanish ancestry is straightforward. African ancestry is strongly supported by the presence of a marker of African descent, Fy, despite the fact that the standard error of the estimate is as large as the estimated admixture proportion. An evaluation of the sensitivity of these results to a number of variables is presented: 1) our choices of ancestral allele frequencies, 2) the possibility of selection at HLA and the blood groups, and 3) genetic drift in Mexican Americans.

Unusual reactivity of several anti-U serums with red cells from RN persons.

Several examples of anti-U were diluted serially and tested with RN red cells and red cells of various Rh phenotypes from both blacks and whites. The agglutination scores were reduced for U+ red cells from people with RN compared with U+ red cells from whites. U+ red cells from blacks yielded score values greater than red cells from people who inherited RN, but definitely less than U+ red cells from whites. The rank-correlation coefficient (0.92) indicated a p value of 0.0005.

An evaluation of 11 red cell elution procedures.

Eleven elution procedures were evaluated for their efficacy in recovering antibody from red cells sensitized with immunoglobulin. The procedures evaluated included eight published methods (Lui, heat, digitonin-acid, ether, chloroform, dichloromethane, xylene, and alcohol freeze-thaw) and three commercial elution kits (EluAid, Ortho Diagnostic Systems, Inc.; Elution Solution, Biological Corporation of America; and Elu-Kit II, Gamma Biologicals, Inc.). The xylene elution method proved to be the most effective method, followed by Elu-Kit II, chloroform, dichloromethane, and digitonin-acid. The other six methods evaluated were not optimal based on the suitability of each procedure and the calculated sensitivity.

An antibody that recognizes a determinant common to S and s-bearing sialoglycoproteins.

We describe an antibody, made by an individual of the phenotype M+, N+, S+, s+, U+, that reacted only with ficin or papain-treated red blood cells, and that initially appeared to have anti-S specificity. However, further studies revealed that the antibody, which did not have anti-U specificity, recognized a determinant present on S+, s-, U+, and S-, s+, U+, but missing from S-, s-, U-, and S-, s-, U+, red blood cells. The specificity of this antibody is discussed in terms of current knowledge of the structure of the Ss sialoglycoprotein.

An investigation of the relationship between the V(hrv), VS, and hrH antigens.

The data from this investigation show that the anti-VS sera studied cannot be separated into anti-hrv (anti-V) and anti-hrH specificities. The antibody specificity is singular and is directed against an antigenic determinant present on VS positive red blood cells. That some anti-VS sera appear to have a separable specificity may be due to the incomplete absorption of those antisera. It was shown that V-, VS+ red blood cells adsorb more anti-VS than do those that are V+, VS+. Several absorption of anti-VS serum with V+, VS+ red blood cells may remove enough of the antibody that the absorbed serum will no longer (visibly) react with V+, VS+ red blood cells, though the same absorbed serum will react with V-, VS+ red blood cells. That this is not a separable specificity can be demonstrated by subsequent absorption to exhaustion of the same serum with V+, VS+ red blood cells. Testing of the original Hernandez serum comfirmed that it defines the antigenic specificity, hrH. The relationship of hrH to VS may be similar to the relationship of the Rh0 (D) antigen to the antigens of the Rh0 (D) mosaic.

Simplified quality assurance of floor model centrifuges.

Present methods for calibration of the rotor speed of large floor model centrifuges used for blood component preparation can be cumbersome and/or dangerous. This report describes a safe and inexpensive method of modifying a centrifuge lid so that calibration of the machine with a photoelectric tachometer is a simple and safe procedure.