Interleukin-12 subunits p35 and p40 of Indian water buffalo (Bubalus bubalis) maintain high sequence homology with those of other ruminants.

The immune system of Indian water buffalo (Bubalus bubalis), one of the major dairy animals of the tropics, has received little attention. cDNAs encoding the two subunits of the heterodimeric interleukin (IL)-12 of Indian water buffalo were isolated from concanavalin A-stimulated lymphocytes. The 710-bp p35 and 1012-bp p40 subunits were amplified by reverse transcriptase polymerase chain reaction (RT-PCR), cloned, sequenced and compared with other ruminant sequences. The IL-12 p35 subunit cDNA had nine nucleotide variations and shared 98.1% amino acid identity with the cattle IL-12 p35. The IL-12 p40 cDNA had 13 nucleotide variations and had 97.5% amino acid identity with the cattle IL-12 p40. Both the subunits showed strict conservation in the predicted secondary structure and critical amino acid residues compared with other ruminant IL-12 molecules. Buffalo IL-12 p40 recombinant protein expressed in Escherichia coli cross-reacted with cattle anti-IL-12 p40 monoclonal antibody. Our study indicates a high level of conservation of this key cytokine among ruminants.