L-Cycloserine is an irreversible inhibitor of 3-ketodihydrosphingosine synthetase, which is the first enzyme of the sphingolipid pathway, and causes the synthesis of sphingolipids to decrease. In vitro studies demonstrated that L-cyloserine inhibits 3-ketodihydrosphingosine synthetase 100 times more than D-Cycloserine .Research regarding L-Cycloserine and its effect on the immune response suggest that L-Cycloserine increases the level of IL-4 producing helper T cells and suppress the adhesion molecules CD29 and CD98. L-Cycloserine also inhibits SPTLC (serine palmitoyltransferase (SPT)), and HIV-1 investigations in the CD4+ lymphoid cell line (CEM) have shown that L-Cycloserine can inhibit HIV-1 replication. L-Cycloserine is an irreversible inhibitor of 3-ketodihydrosphingosine synthetase, which is the first enzyme of the sphingolipid pathway, and causes the synthesis of sphingolipids to decrease. In vitro studies demonstrated that L-cyloserine inhibits 3-ketodihydrosphingosine synthetase 100 times more than D-Cycloserine .Research regarding L-Cycloserine and its effect on the immune response suggest that L-Cycloserine increases the level of IL-4 producing helper T cells and suppress the adhesion molecules CD29 and CD98. L-Cycloserine also inhibits SPTLC (serine palmitoyltransferase (SPT)), and HIV-1 investigations in the CD4+ lymphoid cell line (CEM) have shown that L-Cycloserine can inhibit HIV-1 replication. An irreversible inhibitor of 3-ketodihydrosphingosine synthetase