A method for detecting an inflammatory or an autoimmune condition, comprising analyzing bacterial lipids, such as phosphorylated dihydroceramides (PDHC), in a sample and, comparing results of the analysis of the bacterial lipids in the sample with information on occurrence of the bacterial lipids in a comparable sample, wherein the comparison is indicative of the inflammatory or the autoimmune condition. An example of the autoimmune condition is multiple sclerosis. According to one embodiment, an increased ratio of phosphoglycerol dihydroceramide (PG DHC) to phosphoethanolamine dihydroceramide (PE DHC) in a blood sample indicates a presence of MS in the source patient. The use of PDHCs as biomarkers for detection of MS is described. Antibodies specific to PG DHC or PE DHC are also provided, along with their uses. Also provided are compositions comprising bacteria-originated lipids useful for modulation of immune responses or TLR pathways in humans, animals, and human or animal cells or tissues.
