Cross-reactivity

A two-site immunometric assay of undecapeptide substance P (SP) has been developed. This assay is based on the use of two different antibodies specifically directed against the N- and C-terminal parts of the peptide (95). Affinity-purified polyclonal antibodies raised against the six amino-terminal residues of the molecule were used as capture antibodies. A monoclonal antibody directed against the carboxy terminal part of substance P (SP), covalently coupled to the enzyme acetylcholinesterase, was used as the tracer antibody. The assay is very sensitive, having a detection limit close to 3 pg/mL. The assay is fiiUy specific for SP because cross-reactivity coefficients between 0.01% were observed with other tachykinins, SP derivatives, and SP fragments. The assay can be used to measure the SP content of rat brain extracts. 

The cephalosporins generally cause few side effects (80,132,219—221). Thrombophlebitis occurs as a result of intravenous administration of all cephalosporins. Hypersensitivity reactions related to the cephalosporins are the most common side effects observed, but these are less common than found with the penicillins. Clinically only about 5—10% of patients with allergic reactions to the penicillins manifest the same reactions to the cephalosporins, and data would contradict any tme cross-reactivity to cephalosporins in patients who have previously reacted to penicillin (80,132,219). 

It was established that Ab to Klebsiella pneumoniae didn t demonstrate the cross-reactivity to antigens of the relative bacterial species so, it could be considered that antibodies investigated was highly specific only to the own antigen. The physical-chemical characteristics of the immunological interaction such as constants of formation of Ag-Ab complex were obtained. The binding constants of immune complex were Ka =(9.7 l.l)-10 and Ka,=(1.7+0.3)T0 (mg/ml)f... 

Table 1 Hormonal cross-reactivity of three Type of activity s ...

Specificity of the assay depends on the specificity (cross-reactivity) of the antibodies. Of the known cyanobacterial toxins, only hepatotoxins are detected and are, therefore, able to be screened for by protein phosphatase inhibition. 

As with reverse transcriptase inhibitors, resistance to protease inhibitors may also occur. Mutations in the HIV protease gene were shown to confer resistance to each of the aforementioned molecules. In addition, passaging of viius in the presence of HIV protease inhibitors also gave rise to strains less susceptible to the original inhibitor or cross-reactive to other compounds in the same class. New Diug Targets... 

Aguas, A., Esaguy, N., Sunkel, C.E., Silva, M.T. (1990). Cross-reactivity and sequence homology between the 65 kilodalton mycobacterial heat shock protein and human lactoferrin, transferrin, and DR beta subsets of major histocompatibility complex class II molecules. Infect. Immun. 58, 1461-1470. 

Importantly, the crystal structure of 34 complexed with N9 sialidase (Fig. 8) indicated differences in the orientation of the guanidino group in subsite S2, and in its interaction with the active site residues, compared to that of zanamivir (Babu et al. 2000). These differences have implications for cross-reactivity of 34 with zanamivir-resistant influenza viruses that have Glul 19 mutations in the sialidase S2 subsite (see Sect. 5.1). 

Adedoyin J, Gronlund H, Oman H, Johansson SG, van Hage M Cat IgA, representative of new carbohydrate cross-reactive allergens. J Allergy Chn Immunol 2007 119 640-645. 26... 

Allergy mediated by selective IgE to certain types of NSAIDs by which symptoms are caused exclusively by a specific group of NSAIDs and no cross-reactivity exists with the other groups of anti-inflammatories. In a study carried out with 26 methimazole-allergic patients with IgE-mediated reactions [33], 14 of which developed anaphylaxis, BAT showed a sensitivity of 42% with an optimum specificity of 100%. No other validated in vitro test exists to date for the diagnosis of this disorder and so it represents an essential aid to diagnosis. 

One limitation of serum-specific IgE is that given the cross-reactivity between different Hymenoptera venoms, and also due to the presence of anti-carbohydrate antibodies, it is frequent to find several simultaneous positive results in patients with non-identified insect stings, a situation which makes diagnosis of the same difficult. In these cases, RAST inhibition and the release of histamine occasionally provide data on the venom involved and when this is not the case, it is advisable to administer immunotherapy against both [44]. 

Bumble bee venom contains also a phospholipase A2 with partial identity to bee venom phospholipase Aj and a protease, but no melittin. Instead there are several small peptides called bombolitins [9]. There is limited cross-reactivity between honey bee and bumblebee venoms [2]. 

No sensitization phase Preclinical sensitization to environmental cross-reactive substance... 

Numerous positive delayed skin tests in patients with contrast medium-induced non-immediate skin reactions have been reported when the patients were tested with the culprit contrast medium [summarized in 1]. In a large European multicenter study, 37% of patients with non-immediate reactions were positive in delayed IDEs and/or patch tests [13]. The majority of the patients also reacted to the culprit contrast medium and also to other, structurally similar RCM. Notably, in more than 30% of those skin test-positive patients a RCM had been administered for the first time. Thus, there is a lack of a sensitization phase. Again it may be hypothesized that these previously non-exposed patients may have already been sensitized. Different patterns of RCM cross-reactivity indicate that several chemical entities could be involved. No positive skin tests have been obtained with other contrast medium excipients, such as ethylenediaminetetraacetic acid (EDTA), and only rarely patients have been found to react to inorganic iodide. 

The further allergologic workup is recommended to be performed between 2 and 6 months after the reaction (table 3) [13]. A skin prick test should be performed with undiluted RCM. Afterwards, IDTs with RCM (300-320 mg/ml) diluted 10-fold in sterile saline and reading after 20 min are recommended [13]. As cross-reactivity is frequent, a panel of several different RCM should be tested in an attempt to find a skin test-negative product, which might be tolerated in future RCM examinations. 

A non-allergic mechanism imderlying precipitation of asthmatic attacks by aspirin in hypersensitive patients was proposed over 30 years ago [4]. It was founded on pharmacological inhibition of COX of arachidonic acid and explained a cross-reactivity between different NSAIDs varying in chemical structure. This COX theory was confirmed by several studies [11] and was further refined following discovery of the second COX isoenzyme - COX-2. At least two COX isoenzymes, COX-1 and COX-2, are coded by separate genes. Their role in inflammation, asthma and anaphylaxis has been reviewed previously [12]. 

Schuster C, Wuthrich B Anaphylactic drug reaction to celecoxib and sulfamethoxazole cross-reactivity or coincidence Allergy 2003 58 1072. 

Similarity of venoms among different sea snakes and Elapidae can also be detected immunologically. For instance, the antibody for Enhydrina schistosa showed cross reactivity with the venoms of Hydrophis cyanocinctus, Lapemis hardwickii, and Pelamis platurus 12). The sea snake antivenin not only neutralizes the toxicity of various sea snake venoms, but also Naja naja atra (Taiwan cobra) venom 13-16). The reverse is also true namely, some Elapidae antivenins are also effective for neutralizing sea snake venom lethality 17-19). 

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