This paper examines student engagement in an inquiry-based learning activity, planned to provide students with elements in the social, epistemic and conceptual dimensions related to the scientific practice in Immunology. The activity was applied to 39 groups of students enrolled in Immunology or Biochemistry courses in a public university in Brazil. Students performed data-collection through the execution of an in vitro assay. We analyzed how students represent data and use them to support their claims in their written constructs. To clarify which are the productive epistemologies in students' reports we developed a framework for epistemic practice analysis. Our findings point to a pattern of several epistemic practice categories in their written text, mostly related to the particular contingences of data analysis, rather than to theoretical concepts. In addition, we observed that students performed literary inscriptions to represent their data, however, they tended not to cite all data obtained in their written texts. These results suggest that Immunology education strategies should provide students with approaches that explore the role of data representation in the scientific text rhetoric.