Characterisation of epitopes of pan-IgG/anti-G3m(u) and anti-Fc monoclonal antibodies.

The characterisation of monoclonal antibodies (MAbs) and their epitopes is important prior to their application as molecular probes. In this study, Western blotting using IgG1 Fc and pFc' fragments was employed to screen seven MAbs before pepscan analysis to determine their reactivity to potentially linear epitopes. MAbs PNF69C, PNF110A, X1A11 and MAbs WC2, G7C, JD312, 1A1 detected epitopes within the C(H)3 and C(H)2 domains, respectively. However, only four MAbs showed pepscan profiles that highlighted likely target residues. In particular, MAbs PNF69C and PNF110A that have previously been characterised with pan-IgG and anti-G3m(u) specificity, detected the peptide motif 338-KAKGQPR-344 which was located within the N-terminal region of the C(H)3 domain. Furthermore the majority of residues were present in all four IgG subclasses. Consequently the peptide identified was consistent with the pan-IgG nature of these antibodies. By using PCImdad, a molecular display programme, this sequence was visualised as surface accessible, located in the C(H)2/C(H)3 inter-domain region and proximal to the residue arginine(435). It is speculated that this residue may be important for phenotypic expression of G3m(u) and specificity of these reagents. Pepscan analysis of MAbs G7C and JD312 (both pan-IgG) highlighted the core peptide sequence 290-KPREE-294, which was present in the C(H)2 domain and was common to all four IgG subclasses. PCImdad also showed this region to be highly accessible and was consistent with previous bioinformatic and autoimmune analysis of IgG. Overall these MAbs may serve as useful anti-IgG or anti-G3m(u) reagents and probes of immunoglobulin structure.

Socioeconomic status, C-reactive protein, immune factors, and responses to acute mental stress.

Low socioeconomic status (SES) is associated with increased risk of coronary heart disease and immune-related disorders. We hypothesised that SES would be inversely associated with the acute phase reactant C-reactive protein (CRP) and with circulating lymphocyte levels, and that lymphocyte responses to acute psychological stress would also vary with SES. CRP was obtained from 226, and lymphocyte counts from 127 healthy volunteers from the Whitehall II cohort, and SES was defined primarily by grade of employment. CRP concentration was greater in lower compared with higher SES participants (1.18+/-0.75 vs. 0.75+/-0.8 mg/l,p=.002) independently of sex, age, body mass, waist/hip ratio, smoking, alcohol, and season of the year. Similar differences were evident when SES was defined by income and educational attainment. Higher SES was also associated with lower total lymphocyte (p=.023), T-lymphocyte (p=.024) and natural killer (NK) cell counts (p=.006). Total, T- and B-lymphocyte, and NK cell counts increased with stress, but immune stress reactivity did not vary with SES. Post-stress recovery was delayed in women compared with men. The results suggest that moderate inflammation and immune activation may be processes through which lower SES increases disease risk.