Production and characterization of a monoclonal antibody against the beta-subunit of bullfrog lutropin.

We generated a high-affinity and highly specific monoclonal antibody (BL4B11)-producing hybridoma against bullfrog lutropin (LH) beta by fusing mouse myeloma, X63.Ag8.653, with spleen lymphocytes obtained from BALB/c mice immunized with bullfrog LH-IV (pI 9.3) beta-subunit. The resultant antibody-secreting hybridoma was injected into intraperitoneally pristane-primed BALB/c mice to obtain a large amount of antibody. Noncompetitive binding tests revealed that the ascitic fluid (BL4B11) could be diluted up to 1:12,000 for 50% binding to 125I-labeled bullfrog LH beta and also bound strongly to bullfrog intact LH, but not to LH alpha, follitropin (FSH), FSH alpha, FSH beta, and rat glycoprotein hormones (LH, FSH, and thyrotropin (TSH) significantly. The immunoblotting results also showed a similar immunological specificity of BL4B11. Cross-reactivities of bullfrog LH, FSH beta, FSH, LH alpha, and FSH alpha against BL4B11 were 9.69, 3.76, 2.40, 1, and 1%, respectively, when compared with bullfrog LH beta in the competitive inhibition assay system. The affinity constant (Ka) of the BL4B11 was 1.09 X 10(9) M-1. In the sexually mature bullfrog pituitary, immunoreactive LH cells which were revealed by this BL4B11 were distributed throughout the pars distalis except the rostral region. They were especially large, numerous, and polygonal, with well-developed cytoplasm. In the rostral region, immunoreactive LH cells were larger and more intense than those in the central region. In the case of young bullfrog, several immunoreactive LH cells were found only in the dorsocaudal region of the pars distalis. The distribution and histological characteristics of immunoreactive LH cells were different from those of immunoreactive TSH cells revealed by anti-human TSH beta serum.