Genomics and Applied Biology 2016, Vol.7, No.4, 1-8
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In consistency with other studies (Ploegaert et al. 2010; Ujvari et al. 2011) the current study reported the presence
of Nabs isotypes IgA, IgG and IgM in IC’ serum. This study again confirms that the IgM Nabs isotype is the
major isotype. In previous studies, IgM has accounted for most of the B cell repertoire in the fetus and neonate,
and possibly play a major role in the development and physiology of the mammals B cell repertoire (Boes, 2000).
Most Nabs of the IgM isotype class are present in vertebrates, but IgG and IgA Nabs are also present in higher
vertebrates (Boes, 2000). The Nabs of IgM isotype are mostly produced by CD5+B cells in the peritoneal and
intestinal cavity but also CD5- B cells (Zhou et al., 2004). The other isotypes namely IgA, IgE, IgD and IgG do
arise from IgM class switching and this phenomenon could justify the higher titers of IgM as compared to IgG and
IgA in this study. The choice of Nab in this study is pegged on the fact that it is the natural arm of humoral
immune response, polyreactive and nonspecific in nature (Parmentier et al. 2004). For a parameter to be used as a
potential measure for genetic disease resistance, it should be variable among individual animals. In genetics,
lack of variability of a parameter show that the animals are naturally the same with respect to immune parameter
thus limiting selection (Khobondo et al. 2014). In the current study Nabs binding KLH were found to be
significantly variable among IC and could be exploited in selection for immunoglobulins titre values a proxy for
immune competence. Star et al. (2007) reported Nabs binding KLH to be variable in layers, the same has been
confirmed in other animals like cattle (Ploegaert et al. 2010) and also in this study using IC. The repertoire and
levels of Nabs are dependent on several factors, amongst them is the environment (Kachamakova et al. 2006),
genetic background (Sun et al. 2011) and age (Parmentier et al. 2008; Ujvari et al. 2011). Evidence from various
studies showed Nabs to be genetically controlled (Gonzalez et al. 1989; Sun et al. 2011) and the same is true in the
current study.
Repeatability of IgA, IgG and IgM titres in the context of this study was assessed as well. The purpose was to
ascertain whether a single test on one sample collection was enough for inferences thus reducing the cost of doing
multiple measures. Alternatively repeatability could imply how reproducible or the same a parameter (IgA, IgG or
IgM) were under the same environment and conditions of experiment. This genetic parameter have been useful in
estimating the upper limit of heritability as well. In deed the repeatability estimate for IgM (0.68), IgA (0.99) and
IgG (0.99) were moderate to high. The lower repeatability of IgM experienced in this study was partially expected.
The IgM is the primary or precursor of other antibodies. It could therefore be a more stable isotype with time and
in different or same environment, a deviation from this finding. Thus a higher repeatability of IgM than other
isotypes could be expected under this school of thought. Alternatively, the IgM could represent the continuous
presence of randomly produced antibodies that fit both exogenous and autologous plethora of antigens. The
formation of antibody idiotypes is a random process through recombination or conversion; this could be true with
IgM justifying the class switching role hence lower repeatability evidenced. The low repeatability might also
imply the high turnover that this isotype undergo within a very short duration. It therefore means it is an isotype
on transit and very unstable depending on environmental stimuli and antigen specificity. The genetic interpretation
of the moderate repeatability estimate would imply a large variance between IC (genetic) as compared to variance
within time (environment). This mean that genetic component plays important role in variation observed than
non-genetic factors with regard to IgM antibody titre and repertoires.
The higher repeatability for IgG (0.99) and IgA (0.99) as compared to IgM realized in this study is however
justifiable. This higher estimates could imply lack of plasticity (ie stability) of this isotypes with time and in
different or same environment with respect to KLH (antigen in question), hence the low and high variances within
the sampling period and between IC respectively. The large variance estimate is conferred by the IC (genetic) but
not time period (environment). It has to be kept in mind that this study is the first to determine repeatability of
the anitibody titres in IC and further comparison with other related studies is limiting. The moderate to high
repeatability for both isotypes in this study therefore affirms that a single measurement can be used to infer
reference to Nabs titers of IC along time under same situations/environment with KLH specificity. Thus the result
can be reproduced under same management and conditions of the study and would infer to the ability of what is
observed being reproduced in the next generation under similar management. This eliminates the need to make
