Literature describing the allergens of Prosopis spp. is sparse, with the majority of published research coming from Thakur and fellow scientists in India. Using gel filtration chromatography and polyacrylamide gel electrophoresis with 7.5% gels, Thakur and Sharma separated Prosopis juliflora into six fractions of 13, 20, 27.5, 41, 55.5 and 81 kd . In a guinea pig skin prick test using each of these fractions, they found the 20 kd fraction had major allergenic activity . Using sensitized rabbits, Thakur  found that the 10 and 20 kd fractions were both glycoproteins. Thakur reported a 45% success rate in using both the mesquite crude allergen extract and the 20 kd glycoprotein fraction in human desensitization to Prosopis.
More et al.  used 10–20% gels to investigate the allergens of mesquite in Arizona, USA, and reported IgE responses to 59 and 66 kd proteins in the pollen, wood and wood smoke of mesquite. They commented that more allergens of mesquite pollen were present but did not give further descriptions .
In comparing our results (using 12% gels and pooled human sera for Western blotting) to Thakur's research, we concur with the 20 kd band. The non-specific background in the 20 kd area detected in our negative controls appeared negligible in this study since the optical intensity of the 20 kd band was 89 times stronger than the control.
It is possible that these bands of the present research and Thakur's  (in parentheses) are the same bands: 11 kd (13 kd), 27 kd (27.5 kd), 44 kd (41 kd), 56 kD (55 kd), 71 and 99 kd (81 kd). Discrepancies could be due to the differences in pollen extracts, the concentrations of the gels, the sera used , the accuracy of molecular weight standards or the sensitivity of the detection systems.
In addition to the bands described by Thakur, we found bands at 17, 18, 36 and 64 kd.
The strong 64 kd band present on the blot but not on the gel could be explained by the sensitivities of the detection systems of the gel (500 ng) and the blot (5 pg), differing by a magnitude of 1000. A faint 19 kd band was visible on the blot and on the gel but we did not list it as an separate allergen because it was not distinct from the 20 kd band. This could have been the non-specific background detected in our negative controls. Gel band 14 blotted only faintly and was not included in the total numbers of mesquite allergens in this study.
Before pooling the sera we noticed variation in the reactivity patterns of several of the 10 serum donors at the 56 – 65 levels. When pooled this seemed to result in a blurred area between 56 and 65 kd whereas in individual donors there were clear bands present.
Some donors' sera were missing a band present in other donors. It is possible patients simply have different reactivity patterns to the same pollen or this could be caused by their exposures to variations in Prosopis pollen species. Varieties of Prosopis juliflora in the southwest United States include – glandulosa, Torreyana, and velutina . Prosopis species are morphologically variable, are considered a synagameon (habitual hybridization), and these hybrids are fertile . Patient exposure to mesquite varieties or hybrids could result in different IgE banding patterns, especially when comparing worldwide distributions of Prosopis.
Mesquite (Prosopis juliflora) is considered a serious allergen. Exposure to this pollen in arid areas (both naturally occurring and by intentional plantings), through international travel and military deployment is significant. In addition to pollen exposure, mesquite smoked foods are popular and exposure to mesquite antigens may occur both in food preparation and consumption.
The relevence of cross-reactive mesquite allergens to humans needs serious consideration. The human allergens of mesquite visualized in this study compare favorably to the cross-reactive mesquite allergens we previously described  using mesquite-sensitized rabbits. While this does not necessarily mean that the human allergens to mesquite are cross-reactive, it does suggest the possibility.