Separation of normozoospermic human spermatozoa into subpopulations by selective agglutination with peanut agglutinin

Incubation of human spermatozoa of normozoospermic origin with the galactose specific lectin peanut agglutinin (PNA) resulted in agglutination of the majority of sperm. This finding enabled separation of sperm into two subpopulations. The major one, accounting for 87.0 +/- 12.7 (SD)% consisted of agglutinating sperm (PNA+), while the minor subpopulation (PNA-) did not bind the lectin. The correlation between the percentages of PNA- sperm and acrosome-damaged sperm, as detected by light microscopy prior to separation, was analysed and an overlapping has been found. Light and electron microscopy examination revealed that the PNA- cells were either acrosomeless or possessed severely damaged acrosomes while the PNA+ sperm were mostly free of such pathologies. Following treatment of sperm with fluorescin-conjugated PNA the single cells lacked any labeling while the agglutinates exhibited fluorescence. However, the binding of the lectin to sperm was non-uniform and differences in fluorescence intensity at various parts of the head have been observed. The sialic acid content in PNA+ sperm was found to be significantly higher (7.5 +/- 2.2 micrograms/10(8) sperm) as compared to PNA- sperm (2.1 +/- 0.6 micrograms/10(8) sperm). It was suggested that sialic acid content could be a biochemical indicator of acrosomal integrity. Separation of sperm by selective PNA agglutination might be valuable for elimination of sperm affected by acrosomal pathologies from the ejaculate.