Surfactant protein A
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| surfactant, pulmonary-associated protein A1 | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | SFTPA1 | ||||||
| Alt. symbols | SFTP1 | ||||||
| NCBI gene | 6435 | ||||||
| HGNC | 10798 | ||||||
| OMIM | 178630 | ||||||
| RefSeq | NM_005411 | ||||||
| UniProt | Q8IWL2 | ||||||
| Other data | |||||||
| Locus | Chr. 10 q22.3 | ||||||
| |||||||
| surfactant, pulmonary-associated protein A2B | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | SFTPA2B | ||||||
| NCBI gene | 6436 | ||||||
| HGNC | 10799 | ||||||
| OMIM | 178642 | ||||||
| RefSeq | NM_006926 | ||||||
| UniProt | Q8IWL1 | ||||||
| Other data | |||||||
| Locus | Chr. 10 q22.3 | ||||||
| |||||||
Surfactant protein A is an innate immune system collectin. It is water-soluble and has collagen-like domains similar to SP-D. It is part of the innate immune system and is used to opsonize bacterial cells in the alveoli marking them for phagocytosis by alveolar macrophages. SP-A may also play a role in negative feedback limiting the secretion of pulmonary surfactant. SP-A is not required for pulmonary surfactant to function but does confer immune effects to the organism.[1]
The role of surfactant protein A (SP-A) in childbirth is indicated in studies with mice.[2] Mice which gestate for 19 days typically show signs of SP-A in amniotic fluid at around 16 days. If SP-A is injected into the uterus at 15 days, mice typically deliver early. Inversely, an SP-A inhibitor injection causes notable delays in birth.
The presence of surfactant protein A seemed to trigger an inflammatory response in the uterus of the mice, but later studies found an anti-inflammatory response in humans.[3] In fact, the level of SP-A in a human uterus typically decreases during labor.
Immune functions
Research on SP-A has been done mainly in rodents including mice and rats. This research has shown that mice deficient in SP-A are more susceptible to infections from group B streptoccoal organisms,[4] Pseudomonas aeruginosa,[5] and likely other organisms. The immune functions of SP-A are time-, temperature-, and concentration-dependent.[6]
Location
SP-A is found in the pulmonary surfactant in lungs. SP-A and SP-D are also present in extrapulmonary tissues.[7]
