Immune recognition of cytochrome c I. — Molecular requirements for antibody recognition and immune response stimulation studied in vitro with synthetic peptides

The epitope specificity of antibodies to horse cytochrome c (cyt.c) in the primary and secondary immune response of C57BL mice was studied by means of the ELISA technique with synthetic peptides of cyt.c. It was found that, in the early primary response, N- and C-end fragments of cyt.c (peptides 2–13, 14–22 and 92–104) were preferentially recognized. In the secondary response, more antibodies to the epitopes of the central part of the molecule (peptides 61–69 and 46–56) were found. This was presumed to be due to the mode of cyt.c processing and presentation in the course of immune response: at first, cyt.c was recognized in the native form and then in the processed one. The capacity of cyt.c peptides to stimulate the formation of cyt.c-specific antibody-secreting cells (ASC) was studied in splenocyte culture of C57BL mice. Peptides stimulated more ASC than cyt.c did, but larger molar doses of peptides were required. Comparison of the capacity of related peptides (1–13 and 2–13, 61–69, 61–77 and 57–77) to be recognized by antibodies produced to native cyt.cin vivo and to stimulate anti-cyt.c ASC in vitro suggested certain molecular requirements for cyt.c epitope and agretope formation. These were partially confirmed by computer analysis.