Nickel chelate complexes as a target for polyclonal antibodies raised in rabbits and mice

ABSTRACT

Oral administration of nickel is thought to be responsible for type-IV-mediated mechanism of immune response. Alternative type-I IgE-dependent mechanism is occasionally postulated, given relatively fast onset of symptoms, reports on spontaneous sensitisation and recurring mentions in scientific literature. In this paper, we make an insight into this hypothesis by performing immunisation using nickel(2+) chelates conjugated to carrier proteins, namely nickel coordinated by bifunctional ethylenediaminetetraacetic acid or bifunctional nitrilotriacetic acid, using bovine serum albumin as a carrier (Ni-(ITCB)EDTA-BSA; Ni-(ITCB)NTA-BSA), and nickel coordinated by bifunctional diethylenetriaminepentaacetic acid using bovine serum albumin or keyhole limpet haemocyanin as a carrier (Ni-p-SCN-Bn-DTPA-BSA; Ni-p-SCN-Bn-DTPA-KLH). Antibody raised in mouse as a reaction to Ni-p-SCN-Bn-DTPA-KLH was identified as the most capable of binding Ni(2+)-DTPA with 0.17 nmol nickel recovered per 0.2 nmol pAb, compared to 0.06 nmol Ni purified using reference antibody. Immunoassay methodology was applied upon several modifications to increase antibody contact surface and physical availability of antigen for more efficient binding. Magnetic beads dispersed in free solution were used as a medium for immobilisation and eluted nickel was subject to Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) instrumental quantitative analysis for more precise output reading. The antibody was tested for selectivity against other divalent metals coordinated with DTPA, i.e. Fe, Pb, Zn, Cu, Co and Mn. While Co and Mn were not detected, four other metals, Fe, Pb, Zn and Cu, were eluted in corresponding amounts greater than nickel at 4.15, 1.58, 3.11 and 3.54 nmol. Pb and Ni were the only two antigens whose binding surpassed the level showed by control antibody. We conclude that nickel-based immunogen may show little suitability for in vivo immunisation assays, which reinforces further question about physiological occurrence of potential nickel-responsive IgE antibodies as mediators in type-I hypersensitivity.

KEYWORDS:

• Immunoassay
• antibody
• nickel
• chelate
• magnetic beads

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the National Science Centre Poland (Narodowe Centrum Nauki) under [grant number 2012/05/N/NZ9/01304].