The analysis of 2 x 1 and 2 x 2 contingency tables: an historical review.

This paper describes the historical development of analytic techniques for frequency data presented as 2 x 1 or 2 x 2 contingency tables. The issues raised include: the need for a continuity correction when estimating the exceedance probability of a discrete statistic; the vulnerability of such statistics to a conservative bias when used in hypothesis testing; and the different statistical models that may underlie contingency tables. In the case of 2 x 1 contingency tables the recommended technique is the binomial test with a modified decision procedure for hypothesis testing. In the case of 2 x 2 contingency tables there is a single statistic approximating the chi-square distribution which can be used to test the hypothesis of an association between the two relevant variables and which in most practical situations is robust with respect to the occurrence of small expected cell frequencies

Role of CD4+ and CD8+ T-cells in the induction of oral tolerance to Actinomyces viscosus in mice

Mucosal presentation of Actinomyces viscosus results in the induction of antigen specific systemic suppressor cells in mice. The aim of the present study was to determine the phenotype of the suppressor cells responsible for the induction of oral tolerance to low doses of A. viscosus. When CD8 cell-depleted DBA/2 mice were intragastrically immunized and systemically immunized with A. viscosus, the delayed type hypersensitivity response was suppressed but not the levels of antigen specific serum antibodies. Adoptive transfer of orally tolerized CD4(+) cells to CD4(+)-depleted mice resulted in suppression of delayed type hypersensitivity response but not of the levels of antigen specific serum antibodies. In contrast, adoptive transfer of orally immunized CD8(+) cells to CD8(+)-depleted mice resulted in partially suppressed delayed type hypersensitivity response but significantly inhibited the levels of antigen specific serum antibodies. When orally tolerized CD8(+) cells were cocultured with systemically immunized CD8(+) cell-depleted spleen cells, splenic specific antibodies were inhibited. However, no suppression of splenic specific antibodies could be observed in the cultures containing orally tolerized CD4(+) cells and systemically immunized CD4(+) cell-depleted spleen cells. The results of the present study suggest that oral tolerance of humoral and cellular immunity induced by low doses of A. viscosus may be mediated by CD8(+) and CD4(+) cells, respectively