title: Regulation of murine splenic B cell CR3 expression by complement component 3.
abstract: Complement component C3 has established roles in both innate and adaptive immune responses. C3 cleavage products function in B cell activation through the complement receptors CD21/35. Phenotypes of Ab production between CD21/35(-/-) and C3(-/-) mice are not always congruent, implicating additional roles for C3 in B cell responses. To further characterize complement and complement receptors, we have identified a role for C3 in the regulation of CR3 on splenic B cells. Splenic B2 cells are not defined as expressing CR3, yet the analysis of splenic B cells from C3(-/-) animals demonstrate cell surface expression of CR3. B cells from both wild-type (WT) and C3(-/-) animals express CR3/CD11b/Itgam (integrin alpha M) gene transcripts although the level of such transcripts is 2- to 3-fold higher in B cells from the C3(-/-) animal vs WT cells. C3(-/-) and WT animals have similar B cell subpopulations with identical CR3 expression on B220(-) cells from the spleen, marrow, and lymph nodes. The C3-deficient environment is responsible for altered CR3 expression as WT splenic B cells transferred into C3(-/-) animals expressed cell surface CR3 within 48 h while transfer of C3(-/-) splenic B cells into WT animals depressed surface expression of CR3. Furthermore, transfer of C3-producing splenic macrophages into C3(-/-) mice depressed CR3 expression by resident B cells. These data suggest a role for C3 in influencing the level of expression of CR3 by modulating the transcript levels encoding the CD11b alpha integrin protein.
authors.affiliation: Division of Cell Biology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Jacobson
authors.forename: Kirstin M
authors.initials: KM
authors.lastname: Roundy
authors.forename: Janis J
authors.initials: JJ
authors.lastname: Weis
authors.forename: John H
authors.initials: JH
authors.lastname: Weis
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D039481:CD11b Antigen / Q000235:genetics; D003176:Complement C3 / Q000502:physiology*; D005786:Gene Expression Regulation / Q000276:immunology*; D016177:Macrophage-1 Antigen / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger; D011951:Receptors, Complement / Q000235:genetics; D013154:Spleen / Q000166:cytology*
chemical_list: D039481:CD11b Antigen; D003176:Complement C3; D016177:Macrophage-1 Antigen; D012333:RNA, Messenger; D011951:Receptors, Complement