Protein haptens

The resulting product (II) is subsequently coupled to bovine-serum-albumin in a glycerol-w ater mixture in the presence of dicyclohexylcarbodiimide. The mixture is incubated overnight at 4°C, and the protein-hapten complex is dialysed against distilled water thereby causing its purification. Conjugation of the respective barbiturate to the protein carrier, comparison of the barbiturate BGG-conjugate to control BGG-solution and preparation of 14C-pentobarbital sodium are carried out respectively. 

Cutaneous reactions such as rash or Stevens-Johnson syndrome are also consist with initiation through protein haptenation, although in this case dendritic cell activation/ migration and T-cell propagation are involved [31]. Other immune mediators such as cytokines, nitric oxide and reactive oxygen species which may be linked to the formation of reactive metabolites may also be implicated, as may specific processes occurring at the level of the keratinocyte. 

In vivo, drug-protein (hapten-carrier) complexes can be taken up by APCs, are transported into local draining lymph nodes, and are processed and/or presented to naive T cells by MHCs on APCs. T cells with the appropriate specificity recognize these complexes and are induced to proliferate and expand as primed T cells. In addition, hapten-carrier complexes can be antigenic for B cells. Such hapten-carrier complex-specific B cells, in the presence of T cell help, proliferate and differentiate into plasma cells that produce different antibody isotypes. 

Generally, all soluble immunogens or protein-hapten conjugates are mixed with, emulsified in or adsorbed onto adjuvants. The most widespread adjuvants are (i) Freund s adjuvants (ii) aluminum salts and bentonite (iii) methylated bovine serum albumin and, (iv) heat-inactivated Bordetella pertussis. 

Up to a certain degree, an increase in the dose (weight) of antigen will increase antibody titer however, this may also increase crossreactivity. Adjuvants also increase the immunogenicity of proteins. Haptens should be labeled with carrier proteins to elicit an immune response. The carrier protein should be foreign to the host to be recognized by the T-cells. For most immunogens, the interaction of T- and B-cells is essential for antibody production. 

Figure 2 Schematic of a carrier protein-hapten conjugate.

Much of our insight into the nature of antibody specificity has been acquired through experiments in which haptens were tested for their capacity to inhibit the precipitin reaction of antihapten antibody with a protein-hapten conjugate. The method was exploited for many years by K. Landsteiner and his collaborators, who combined ingenuity with enormous energy and established many of the basic principles of antibody specificity. Their work is summarized in a book published by Landsteiner in 1944 (1), near the end of his career. In the early 1940 s... 

Fig. 2.1. Mechanism of inhibition by free hapten molecules of the precipitation of an antihapten antibody with a protein-hapten conjugate. Inhibition is attributable to the large excess of free molecules as compared to those bound to the carrier protein.

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