| Disease susceptibility in newly hatched chicks is due, in part, to the immaturity of the immune system. A thorough understanding of gene regulatory pathways that control the development of the immune system would benefit disease control, which is a major concern to the poultry industry. Gene expression in chicken thymic T cells during late embryogenesis and early growth was examined using DNA microarrays. Gene expression patterns were profiled into 9 clusters using self-organizing maps cluster analysis. Expression of cell surface markers (MHC class I alpha-chain, MHC class II invariant gamma-chain, CD8, CD18, and beta2 microglobulin), and genes involved in the innate immune response (granulysin) increased with age, and these patterns were consistent with an increase in the immune-responsiveness of the young chick. The expression of IL2 receptor gammac and TCR alpha-chain increased up to 1-day and then decreased. A recently characterized apoptosis-related gene, LARD, was downregulated after E16 and thereafter upregulated at 1-day.; Forty genes were identified as abundantly expressed genes in thymic T cells by microarray assay. Several commonly expressed housekeeping genes (ubiquitin, elongation factor alpha, and cyclophilin A) and a number of lymphoid tissue-related genes (ICSBP, Spi-1/PU.1 transcription factor, and leukocyte immunoglubulin-like receptor) were identified. Of the 40 genes, seven overlapped with those characterized by the "EST clone counting" of a T cell library.; Changes in response to MD vaccine HVT were compared with in ovo versus day-of-hatching subcutaneous vaccination protocols. Three genes, stem cell antigen 2, interferon inducible protein, and acetylCoA transporter, which were induced at 1-day after in ovo vaccination, showed significantly high level of expression in thymic T cells purified from 1-week-old chickens subcutaneously vaccinated with HVT at hatching. This indicates the acceleration of early immune responses by in ovo vaccination. Compared to serotype 3 MDV vaccine HVT, a serotype 1 vaccine CVI988 induced several more tumor/transformation-related genes, including NF kappa B2, MASL1, and MSH6. This difference suggests that CVI988 elicits chicken immune responses related to tumor/transformation. These gene profiling studies will provide basic understanding of the immune system, as well as provide novel tools for predicting vaccine efficacy and immuno-responsiveness. |
