Antibodies with the cell-type specificity to the morula cells of the solitary ascidians Styela rustica and Boltenia echinata.

The separation of the blood cells of Styela rustica (Styelidae, Stolidobranchiae) in discontinuous Percoll gradient showed 4 fractions. The 4th and bottom most fraction contained 90-100% of morula cells. The protein composition of the morula cell fraction revealed on SDS-PAGE showed two major proteins with m.w. 47 and 26 kDa. These proteins were heavily positively charged. Polyclonal antiserums against these proteins were raised. Each antiserum reacted with both proteins only in morula cells on the blot after SDS-PAGE and stained the proper protein without crossreaction on the blot after AU-PAGE. The only type of cells stained with antibodies in circulating blood, in the tunic and on the tunic wound surface in paraffin sections of another species Boltenia echinata (Pyuridae, Stolidobranchiae) were morula cells. The morula-type specific antibodies obtained recognized major positively charged proteins which were apparently structural substrates for the phenoloxidase tanning.