We identified these two peaks, with mass to charge ratios (m/z) of 9,100 and 10,100, as anaphylatoxin C3a and calgranulin A by additional mass spectral investigation using liquid chromatography coupled to mass spectrometry.
The two lowest bands (Figure 2, bands 1 and 2) likely correspond to the SELDI-TOF peaks with m/z 9,100 and 10,100 and were identified by database searches as anaphylatoxin C3a and calgranulin A.
Two readily observable peaks, seen only in spectra from the diesel-exposed, 24-hr samples, represent anaphylatoxin C3a and calgranulin A, and a third peak, whose signal is only slightly above noise, is also present only in spectra from exposed, 24-hr samples and was identified as calgranulin B.
Subsequent analysis using LC/MS indicates that the proteins producing these peaks are calgranulin A, calgranulin B, and anaphylatoxin C3a.
Anaphylatoxin C3a, a component of the complement system, is a well-known mediator of inflammation [see Ember and Hugli (1997) for a review], and calgranulin A is a part of a hetero-dimer with calgranulin B (also known as MRP-8 and MRP-14, respectively) that make up calprotectin.