Abstract
Surfactant Protein D (SP-D) is a multifunctional protein present in the lung and in respiratory secretions. In the process of developing new experimental approaches to examine SP-D function, we observed that SP-D adsorbs to polypropylene tubes to a great extent, thereby depleting SP-D from the solution. Although it is well known that proteins adsorb nonspecifically to plastic, this effect is usually diminished by treatments to make the plastic “low-retention” or “low-binding”. However, these treatments actually increased the binding of SP-D to the plastic. In addition, this adsorption affected the results of several assays, including proteolytic cleavage assays. In order to block SP-D from adsorbing to polypropylene and the effects caused by this adsorption, we coated the tubes with bovine serum albumin (BSA), as is commonly performed for ELISAs. This coating greatly diminished the amount of SP-D sticking to the plastic, providing an inexpensive and effective method for preventing adsorption and the artifacts resulting from this adsorption.
Highlights
Surfactant protein D (SP-D) is a pulmonary collectin that has various roles in the lung, including surfactant homeostasis, regulation of inflammation, and innate host defense
In order to determine whether this was due to a decrease in the SP-D content of the solution, we examined the levels of SP-D in the supernatant of the solutions after incubations in the tubes (Figure 2)
Much work has been done to elucidate the functions and properties of SP-D, and this continues to be an active arena of research
Summary
Surfactant protein D (SP-D) is a pulmonary collectin that has various roles in the lung, including surfactant homeostasis, regulation of inflammation, and innate host defense (reviewed in [1]). While several studies have only examined levels using an ELISA format, others have shown that the structural state of SP-D is altered in many pulmonary diseases through the use of western blotting. These studies show that SP-D can be fragmented in the human lung [4,5], and further research has described several proteases which have the ability to cleave SP-D. The use of SP-D as a biomarker for various diseases/severity of disease is being explored
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