Virulence factor that plays an important role in immune evasion. Lyses human lymphocytes and monocytes. Binds to the LFA-1 integrin on the surface of the host cell and to cholesterol-containing membranes, which probably results in large LtxA-LFA-1 clusters in lipid rafts. Shows also beta-hemolytic activity on certain types of growth media. Interacts specifically with the superoxide dismutase [Cu-Zn]. This interaction may protect LtxA from reactive oxygen species and reactive nitrogen species produced by host inflammatory cells during disease (PubMed:17635874). Interacts with the human leukocyte adhesion glycoprotein LFA-1 (ITGAL-ITGB2) (PubMed:17635865). Leukotoxin expressed by the rough, adherent, clinical isolate CU1000N is cell associated. However, smooth, nonadherent strains, including Y4, JP2 and CU1060N, secrete an abundance of leukotoxin into the culture supernatants during early stages of growth (PubMed:11035711). Secretion is inhibited by free iron (PubMed:17041062). Levels of toxin expression vary greatly among strains. Highly leukotoxic strains (JP2-type strains) produce more LtxA protein and ltx mRNA than minimally leukotoxic strains (652-type strains). Variations are probably due to different types of promoters (PubMed:8300209). Expression is not affected by iron (PubMed:17041062). The Gly-rich region is probably involved in binding calcium, which is required for target cell-binding or cytolytic activity. Acylated at Lys-562 and Lys-687 by LtxC. This modification is required for full activity. Isolated methyl esters contain palmitoyl and palmitolyl fatty acyl groups with smaller quantities of myristic and stearic fatty acids. Mutation completely abolishes the beta-hemolytic activity of A.actinomycetemcomitans. Belongs to the RTX prokaryotic toxin (TC 1.C.11) family.