ABO phenotype protected reproduction as it is based on fucosylations.

The molecular biological relationship between human fertility and ABO(H) blood group phenotype formation becomes evident with the rare (Oh) or <i>Bombay</i> blood type, which based on the history of his own family, Charles Darwin would have interpreted as resulting from reduced fertility in consanguinities. In its native form, the <i>Bombay</i> type occurs in individuals with an extremely rare genotype (h/h;se/se), by which the fucosyltransferases FUT1 and FUT2 are not produced due to point mutations. These enzymes, encoded on chromosome 19, are epistatically connected with the A and B allelic glycotransferase functions encoded on chromosome 9, while the fucosyl residues provide the functional-structural basis for the formation of any ABO(H) phenotype on the cell surface or in secretions and plasma proteins. Immunoglobulins are also heavily fucosylated, and via developmental variation of the positions between the cell surfaces and the heavy chains of immunoglobulins, fucosyl residues appear to augment or reduce antibody-mediated cellular cytotoxicity involving physiological anti-self-reactivity; moreover, by regulating the assembly and intracellular signaling of precursor B cell receptors, the core fucosylation of immunoglobulin heavy chains represents a key mechanism in clonal selection. In fact, the seminal plasma of leucospermic infertile men has been reported to exert high levels of poorly core-fucosylated IgG. Consequently, in <i>Bombay </i>type individuals, the non-somatic glycosylation processes of embryogenic stem cell-to-germ cell transformation, which involve the modification and <i>O</i>-fucosylation of epidermal growth factor (EGF), are most likely exposed to metabolic competition with multiple glycosidic sites of poorly fucosylated, glycan-depleted immunoglobulins that might promote increased anti-self-reactive cytotoxicity.

人类生育力与ABO(H)血型表型形成之间的分子生物学关联，在罕见的Oh血型（Oh）或孟买血型（Bombay）中体现得尤为清晰。基于自身家族史，查尔斯·达尔文本会将此类血型归因于近亲婚配所导致的生育力降低。天然状态下，孟买血型（Bombay）见于携带极为罕见基因型（h/h;se/se）的个体，该基因型因点突变无法合成岩藻糖基转移酶（fucosyltransferase）FUT1与FUT2。这两种由19号染色体编码的酶，与9号染色体上编码的A、B等位基因糖基转移酶（glycotransferase）功能存在上位性关联；而岩藻糖残基（fucosyl residues）为细胞表面、分泌物及血浆蛋白上任一ABO(H)表型的形成提供了功能结构基础。免疫球蛋白（Immunoglobulin）同样会发生广泛的岩藻糖基化，且通过细胞表面与免疫球蛋白重链之间的位置发育变异，岩藻糖残基似乎能够增强或减弱涉及生理性自身反应性的抗体介导细胞毒性（antibody-mediated cellular cytotoxicity）。此外，通过调节前体B细胞受体的组装与细胞内信号转导，免疫球蛋白重链的核心岩藻糖基化是克隆选择（clonal selection）的关键机制。事实上，已有研究报道伴白细胞精子症的不育男性的精浆中，存在大量核心岩藻糖基化不全的免疫球蛋白G（IgG）。因此，在孟买血型（Bombay）个体中，涉及表皮生长因子（EGF）修饰与O-岩藻糖基化（O-fucosylation）的胚胎干细胞向生殖细胞转化过程中的非体细胞糖基化途径，极有可能与大量岩藻糖基化不全、聚糖缺失的免疫球蛋白的多个糖苷位点（glycosidic sites）产生代谢竞争，进而可能促进自身反应性细胞毒性的增强。