Adhesion of hemocytes to desialylated prothoracic glands of Galleria mellonella (Lepidoptera) in the larval stage

Earlier work showed the existence of sialic acid (SA) in the prothoracic gl ands (PGs) of Galleria mellonella (Karacali et al., 1997). In this paper we investigated the role of SA during the degeneration process of PGs. Neuram inidase-digested larval PGs were incubated within the hemolymph collected f rom same age larvae. Light and electron microscopic observations showed inc omplete capsule formation by the accumulation of hemocytes around desialyla ted gland cells, but not in the control group. Desialylated larval PG cells were recognized as a foreign structure or non-self by hemocytes. The resul t indicates that SA acts as a mask for hemocytic receptors during the larva l period under normal conditions. However, in the absence of SA, the glands start to degenerate. We provide an explanation for the role of SA in the r ecognition process of hemocytes that initiates the degeneration of PGs in p upal cells and show the functionality of SA in insects, confirming that SA is a universal molecule.