Search

The reported linkage between cutaneous melanoma and the dysplastic nevus syndrome (CM/DNS) to markers located on the distal portion of the short arm of chromosome 1 was examined in three Utah kindreds ascertained for multiple cases of melanoma. Family members in these kindreds were genotyped for the two markers reported to be most closely linked in the Bale study, PND and D1S47. Both melanoma alone and a combined melanoma/DNS phenotype were analyzed; no evidence for linkage was found. By multipoint linkage analysis the CM/DNS locus was excluded from an area of 55 cM containing the PND-D1S47 region. Diagnostic or genetic heterogeneity are alternate explanations for the discrepancy between our observations and those of Bale et al.

Two forms of intestinal alkaline phosphatase have been recognized in humans. They are very similar in a number of biochemical and immunologic characteristics, but the exact genetic relationship between them remains unclear. To further study this problem, six monoclonal antibodies and a polyclonal rabbit antiserum to human fetal intestinal alkaline phosphatase have been produced. All of the monoclonal antibodies and the rabbit antiserum crossreact with adult intestinal alkaline phosphatase and with the intestinal-like alkaline phosphatase found in D98/AH-2 human tissue-culture cells. Four of the monoclonal antibodies and the rabbit antiserum crossreact with placental alkaline phosphatase, while none of the antibodies or the antiserum recognize liver or kidney alkaline phosphatase. Four of the monoclonal antibodies can distinguish between adult and fetal intestinal alkaline phosphatase in electrophoretic titration-binding studies, with the relative binding of adult enzyme being significantly greater than that of the fetal enzyme in each case. One of these antibodies, which also reacts with placental alkaline phosphatase, can distinguish the type 3 allelic variant of the placental enzyme from types 1 and 2. This indicates that the antibody detects a structural difference in the protein moiety of one of the allelic forms of the enzyme. These data suggest that adult and fetal intestinal alkaline phosphatases represent structurally distinct proteins, either encoded for by different genes or produced by differential processing of a common precursor molecule determined by a single gene.

Eighteen monoclonal antibodies were produced by the mouse hybridoma method using purified placental alkaline phosphatase (ALP) as antigen. The ability of the various antibodies to discriminate among allelic variants of the enzyme was tested using a large panel of placental ALPs that had been typed electrophoretically. The panel included sets of samples of each of the six common polymorphic phenotypes as well as a series of rare variants. The reactivity of each antibody with each placental ALP (binding ratio) was determined relative to a single standard placental ALP (type 1) in a quantitative binding assay. The findings for six of the antibodies have already been reported. The results on the other 12 antibodies are presented here, and the combined data on the total series of 18 antibodies are analyzed and discussed. Six of the 18 antibodies showed significantly reduced binding to one or another of the products of the three common alleles. In three cases, the discrimination was reflected by essentially "all-or-none" binding reactions. In the other three cases, the binding differences were less marked but could be demonstrated by quantitative comparisons of the binding ratios. Quantitative binding ratio comparisons also enabled heterozygotes to be differentiated from homozygotes in each case. Some of the antibodies showed reduced binding with certain of the rare variant ALP electrophoretic phenotypes. It is estimated that at a minimum this unselected series of 18 antibodies is directed to at least nine different antigenic determinants on the surface of the placental ALP molecule. The results illustrate the power of monoclonal antibodies to discriminate among allelic variants of enzymes.