ABO phenotype protected reproduction as it is based on specific fucosylations.

The molecular biological relationship between human fertility and the formation of the ABO(H) blood group phenotype is evident in the rare (Oh) or <i>Bombay</i> blood type, which, based on the history of his own family, the <i>Darwin/Wedgewood Dynasty</i>, 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), in whom the fucosyltransferases FUT1 and FUT2 are not produced due to point mutations. These enzymes, which are encoded on chromosome 19, are epistatically connected with the A and B allelic glycotransferase functions encoded on chromosome 9, and 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 fucosyl residues appear, via developmental variations in their positions on cell surfaces and on the heavy chains of immunoglobulins, to increase or reduce antibody-mediated cellular cytotoxicity involving physiological anti-self-reactivity; moreover, by regulating the assembly and intracellular signalling 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 leukospermic infertile men has been reported to exhibit high levels of poorly core-fucosylated IgG. Thus, when antibody-dependent cellular cytotoxicity can be increased 50-fold simply by removing the single fucose residue from the Fc glycan, in <i>Bombay </i>type individuals, the non-somatic glycosylation processes of embryogenic stem cell-to-germ cell transformation are most likely exposed to metabolic competition with multiple glycosidic sites of poorly fucosylated, glycan-depleted immunoglobulins, suggesting to promote anti-self-reactive cellular cytotoxicity in male gamete performance.人类生育能力与ABO(H)血型表型（ABO(H) blood group phenotype）形成之间的分子生物学关联，在罕见的Oh型或称孟买（Bombay）血型中体现得尤为显著。基于自身家族史，查尔斯·达尔文（Charles Darwin）或许会将达尔文/韦奇伍德王朝（Darwin/Wedgewood Dynasty）个体出现的此类血型，归因于近亲婚配导致的生育力下降。孟买血型的天然表型仅见于携带极罕见基因型（h/h;se/se）的个体：由于点突变（point mutations），这类个体无法产生岩藻糖基转移酶（fucosyltransferases）FUT1与FUT2。这两种酶由19号染色体编码，与9号染色体上编码的A、B等位基因糖基转移酶（allelic glycotransferase）功能存在上位性关联；岩藻糖残基（fucosyl residues）则为细胞表面、分泌液及血浆蛋白上任何ABO(H)血型表型的形成提供了功能结构基础。免疫球蛋白（immunoglobulins）同样存在大量岩藻糖基化修饰，岩藻糖残基通过其在细胞表面及免疫球蛋白重链（heavy chains）上的位置变化，可增强或减弱介导自身生理反应的抗体依赖性细胞毒性（antibody-mediated cellular cytotoxicity）；此外，免疫球蛋白重链的核心岩藻糖基化通过调控前B细胞受体的组装与胞内信号传导（intracellular signalling），成为克隆选择（clonal selection）的关键机制。已有研究报道，白细胞精子症不育男性（leukospermic infertile men）的精浆（seminal plasma）中，存在大量核心岩藻糖基化程度低下的IgG。事实上，仅需移除Fc聚糖（Fc glycan）上的单个岩藻糖残基，抗体依赖性细胞毒性即可提升50倍。因此，在孟买血型个体体内，生殖干细胞（embryogenic stem cell）向生殖细胞（germ cell）转化过程中的非体细胞糖基化过程，极有可能与大量岩藻糖缺乏、聚糖缺失的免疫球蛋白产生代谢竞争，进而提示该过程会促进针对雄性配子（male gamete）功能的自身反应性细胞毒性。