Methods for detecting inflammatory or autoimmune conditions, comprising analyzing bacterial L-serine containing lipids in a sample； and, comparing results of the analysis of the bacterial L-serine containing lipids in the sample with information on occurrence of the bacterial L-serine containing lipids in a control sample, wherein a decreased occurrence of the bacterial L-serine containing lipids in the test sample over the occurrence of bacterial L-serine containing lipids in the control sample indicates the presence of an inflammatory or an autoimmune condition, are described herein. An example of the autoimmune condition is multiple sclerosis (MS). The use of bacterial L-serine containing lipids as biomarkers for detection of MS is described. Antibodies specific to L-serine containing lipids and their uses are also provided. Also provided are compositions comprising bacterial L-serine containing lipids for modulating immune responses or TLR pathways in humans, animals, and human or animal cells or tissues.
