Newly exposed immunochemically cross-reactive epitopes in sperm-specific LDH after glucosylation and gossypol interaction

PROBLEM: In a previous study, mouse lactate dehydrogenase-C-4 (LDH-C-4) aft er chemical modifications with gossypol (Gossy-LDH-C-4) and glucosylation w ith lactose (Glu-LDH-C-4) was found to induce high immunological infertilit y in allogenic mice. In the present study, the characterization of antibodi es and cross reactivity of the antisera produced against Gossy- and Glu-LDH -C-4 with purified somatic isozymes are being reported. METHODS: Allo-antisera generated in Balb/c mice (i.r. route) against one pr imary (50 mug) and two secondary doses (30 x 2 mug) in Al(OH)(3) were teste d for cross-reactivity by ELISA and antibody avidity using Scatchard plot a nd Sip's plot. RESULTS: Results suggested that IgG against native LDH-C-4 failed to recogn ize somatic isozyme, while antisera against chemically modified LDH-C-4 con sistently reacted with purified LDH from kidney and placenta. Scatchard plo ts and antibody saturation curves of native and complexed LDH supported the presence of heterogenous antibodies with a mean association constant (Ka) of the order of 10(6) - 10(7) M-1 whereas diversity of heterogeneity, defin ed by diversity constant (a), ranged between 0.89 and 1.23. In general, ant i-Glu-LDH-C-4 antiserum and native LDH-C-4. reacted with higher Ka (low aff inity) with a diversity constant of 0.89 compared with interaction between native LDH-C-4 and it's antibodies. CONCLUSIONS: It is concluded that LDH-C-4 is not an immunochemically sperm- specific protein, in which crossreactive epitopes are hidden within its con formation. Due to the large intake of cotton seed (a source of gossypol) by cattle, its unrefined oil by humans in various parts of the world, and the prevelance of diabetic state all the world over, the present study warns o f immunological consequences in situ following gossypol interaction and glu cosylation of LDH and conformationally related proteins in circulation.