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.

人类生育力与ABO(H)血型表型（ABO(H) blood group phenotype）之间的分子生物学关联，在罕见的Oh型或孟买（Bombay）血型中体现得尤为显著。基于自身家族史——达尔文/韦奇伍德王朝（Darwin/Wedgewood Dynasty）的家族史，查尔斯·达尔文（Charles Darwin）或许会将此类血型的出现归因于近亲婚配导致的生育力降低。天然状态下的孟买血型见于携带极为罕见基因型（h/h;se/se）的个体，这类个体因点突变无法合成岩藻糖基转移酶FUT1与FUT2。这两种由19号染色体（chromosome 19）编码的酶，与9号染色体（chromosome 9）上编码的A、B等位基因糖基转移酶功能存在上位性关联；岩藻糖残基则为细胞表面、分泌物及血浆蛋白上各类ABO(H)表型的形成提供了功能结构基础。免疫球蛋白同样存在高度岩藻糖基化修饰；岩藻糖残基可通过其在细胞表面及免疫球蛋白重链上的位置发育变化，增强或减弱涉及生理性自身反应性的抗体介导细胞毒性。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过程中的关键调控机制。事实上，已有研究报道，白细胞精子症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，当仅通过去除Fc聚糖（Fc glycan）上的单个岩藻糖残基即可使抗体依赖性细胞毒性提升50倍时，孟买血型个体体内，胚胎发生干细胞（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不足、聚糖缺失的免疫球蛋白发生代谢竞争，这提示该过程会促进针对男性配子（male gamete）功能的自身反应性细胞毒性。