T-cell-dependent antibody response

The current practice of using a T-cell-dependent antibody response or natural killer cell function is based on analyses suggesting that these parameters would suffice to identify the vast majority of immunotoxicants.12 However, it is clear that there are exceptions12 and that some immunotoxicants are not effectively identified by these functional tests or by histopathology.3 Thus, it remains possible, particularly if the cost of microarray analysis decreases, that microarrays will eventually prove to be the most practical method available to identify immunotoxicants. 

Immunogenicity can be identified by identifying potential antibodies in plasma. These usually involve ELISA methods. T-cell-dependent antibody responses can be evaluated, and plaque assays involving IgM antibody responses are available. 

Two organochlorine pesticides have also been evaluated in animal models using early life stage exposures. Methoxychlor (Chapin et al., 1997) and heptachlor (Smialowicz et al., 2001) were evaluated for immunotoxicity after perinatal plus juvenile exposure of rats. In the case of methoxychlor, T cell-dependent antibody responses were depressed persistently in males but not females (Chapin et al., 1997). For heptachlor, early exposure of Sprague-Dawley rats, using doses relevant to human exposure, produced persistent impairment of antibody responses in males but not females. No adult-exposure immunotoxicity was observed at the doses examined, suggesting that there is an increased susceptibility of the prenatal and/or early postnatal life stages to this pesticide (Smialowicz et al., 2001 Smialowicz, 2002). 

The T cell dependent antibody response to immunization with SRBC or KLH. 

TDAR = T cell dependent antibody response, DTH (=delayed-type hypersensitivity test) is problematic in NHP. 

Whereas the experimental design is quite standardized regarding maternal aspects, the duration of postnatal infant assessments is rather variable between studies, for example, from 7 days to 720 days in our experience. Evidently there is a need for standardization of the timing and type of test batteries for infants and of the time period the infant should be raised. For behavioral tests, a postnatal observation period of 9 months appears essential since these tests can only by applied from the age of 6 months onward. For evaluation of immune system development, a period of 6 months appears mandatory since from that age onward blood volume is sufficient to conduct several tests, such as the T cell dependent antibody response (TDAR), NK cell... 

Figure 18.2 T-cell dependent antibody response in immature cynomolgus monkeys at various postnatal ages. Keyhole limpet hemocyanin (KLH) was administered intrader-mally at 100 jLLg in Freunds s incomplete adjuvant. Note that a clear antibody response is present at about 3 months of age followed by an increased response after second immunization at about 6 months of age. Data represent mean values + SEM of 5 to 6 animals (males and females combined).

Purpose Timeline What is the T cell dependent antibody response to KLFI (keyhole limpet hemocyanin) in the monkey (Note this design may be incorporated with other short-term monkey studies)... 

If the weight-of-evidence review indicates that additional immunotoxicity studies are needed, there are a number of assays which can be used. It is recommended that an immune function study be conducted, such as a T-cell dependent antibody response (TDAR). If specific cell types are affected in STS not involving cells participating in a TDAR, assays that measure... 

In experimental mouse studies, TCDD exposure results in thymic atrophy and alterations in an array of adaptive immune responses including delayed-type hypersensitivity (DTH), cytotoxic T lymphocyte (CTL) activity, and T-cell-dependent antibody responses. In contrast, TCDD enhances neutrophil recruitment to the site of antigen challenge. Because both cell-mediated and humoral immunity are suppressed by TCDD and related HAHs, it is not surprising that administration of these compounds to mice results in increased susceptibility to challenge with viral, bacterial, or parasitic diseases, as well as syngeneic tumors. 

Currently, a heptavalent vaccine (Prevnar) is available for use in children. This vaccine contains the conjugated capsular polysaccharides of serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F, which cause approximately 80% of pediatric pneumococcal bacteremias in the United States. The vaccine elicits a primary T-cell-dependent antibody response with the first dose and an immunologic memory effect after four doses. 

Lussow AR, MacDonald HR Differential effects of superantigen-induced anergy on priming and effector stages of a T cell-dependent antibody response. Eur J Immunol 1994 24 445 449. 

Splenic T-cells were cultured in vitro with antibody T-cell receptor T cells from JP-8-exposed mice had reduced proliferative response T-cell-dependent antibody responses to KLH antigen injected in Freund s adjuvant were not altered by exposure to JP-8... 

Piccotti JR, Alvey JD, Reindel JF, Guzman RE. T-cell-dependent antibody response assay development in cynomolgus monkeys. J Immunotoxicol 2005 2 191-196. 

Much of the earlier work that showed a high concordance for the ability of lymphocyte subset enumeration to predict immunotoxicity (more specifically immunosuppression) was obtained from studies of environmental chemicals and pesticides in mice. More recently, a growing number of publications have also shown agreement between alterations in peripheral blood or splenic lymphocyte subsets and decreased T cell-dependent antibody responses and/... 

Kurogi K, Naohara K, Kouchi M, Aoki Y, Tanaka K, Yasuba M. Assessment of T-cell-dependent antibody response, hematology, pathology and immunophenotyping in the identical rat on immunotoxicology studies. J Toxicol Sci 2005 30(Suppl) S69. 

The objective of this section is to provide a description of several immune parameters and methodologies that are used in the preclinical setting to characterize immune hazards for human risk assessments. The utility of a standalone functional evaluation, specifically the rat T cell-dependent antibody response (TDAR) model developed for regulated immunotoxicity evaluations (Gore et al, 2004), is mainly used for hazard identification, i.e., unintended immunosuppression. This assay is based on an end point parameter that is the... 

Evaluation of a T cell-dependent antibody response (TDAR) is a critical component of the evaluation of immune function in the neonates. In this assay, neonates are injected with a T-dependent antigen, usually keyhole hmpet hemocyanin (KLH) or tetanus toxoid ( ITX), and the development of antibodies is measured over time. In monkeys there can be high inter-animal variability so the collection of serial blood samples is important and the data can be expressed as the area under the antibody titer versus time curve. Figure... 

Kim CJ, Berlin JA, Bugelski PJ, Haley P, Herzyk DJ. Combined analyses of heterogeneous immunotoxicology studies using functional T cell-dependent antibody response tests. Perspect Exp Clin Immunotoxicol 2007 1 60-73. 

Joseph R. Piccotti, PhD, Fellow, Immunotoxicology, Drug Safety and Metabolism, Schering-Plough Research Institute, 556 Morris Avenue, Summit, NJ 07901, Email joseph.piccotti spcorp.com Chaper 3.1.1 T-Cell Dependent Antibody Response Tests... 

Lehrec H, Molinier B, Boverhof D, Collinge M, Freebem W, Henson K, et al. The T-cell-dependent antibody response assay in nonclinical studies of pharmaceuticals and chemicals study design, data analysis, interpretation. Regulatory Toxicology and Pharmacology. 2014 69(1) 7-21. 

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