Use of mannosylglycerate and its derivatives as immunostimulating agent

The present invention relates to compounds of general formula (I) wherein n represents an integer between 0 and 3, preferably n is 0; X represents O, NR3 or S, preferably X is O, R1 is CO2R4, COR4, CH2OR4, C (O) NR4R5, C (O) N (OR 5) R 4, CH2NR4R5, P (O) (OR4) (OR5), P (O) (OR4) R5, SO2 (OR4) or SO2NR4R5, R2 is H, (C1-C6) alkyl, OR6, CH2OR6 or CH2NR6R7, and R3, R4, R5, R6 and R7 are each independently other, H or (C1-C6) alkyl, process for their manufacture and their use as immunostimulant, especially for preventing and treating neoplastic and infectious diseases.