Human T-helper clones induce IgG production in a subclass-specific fashion.
The mechanisms governing the induction of IgG subclasses by T-helper cells in humans were investigated. As preliminary bulk-culture experiments had indicated that a direct B cell contact with viable T cells was an essential requirement for optimal IgG subclass production, 256 CD4+ human T cell clones were preactivated with PHA and cultured in direct contact with autologous B cells. These clones induced IgG production in a strikingly subclass-specific fashion. Moreover, the distribution of subclass-specific helper clones was very similar to the IgG subclass profile observed in serum and peripheral lymphoid tissue plasma cells (IgG1 approximately 60%, IgG2 approximately 30%, IgG3 approximately 5-10%, IgG4 less than or equal to 5%) and unlike that observed in resting B cells (which is IgG1 approximately 40% and IgG2 approximately 50%). It would, therefore, seem that a predominance of T cells capable of delivering IgG1-specific, as opposed to IgG2-specific, help is an essential factor for the preferential induction of IgG1 antibodies during B cell proliferation and differentiation. There was no relationship between IL2, IL4, IL6, and IFN-gamma secreted by the T-helper clones and their IgG subclass induction patterns. In addition, only a few supernatants were able to reproduce the helper effects of the clones themselves. Therefore, direct contact of B cells with helper clones is crucial for IgG-subclass production in humans.
Dembech
C
C
Department of Medicine, University of Perugia, Italy.
Quinti
I
I
Cimignoli
E
E
Albi
N
N
Terenzi
A
A
Gerli
R
R
Galandrini
R
R
Grignani
F
F
Velardi
A
A
D001402:B-Lymphocytes / Q000276:immunology*; D015704:CD4 Antigens; D002450:Cell Communication; D002999:Clone Cells / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis*; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis*; D011043:Pokeweed Mitogens; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
D015704:CD4 Antigens; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D011043:Pokeweed Mitogens