Gitta obtained her PhD in Biology at the University of Mainz and then did postdoctoral studies in London and Cambridge, followed by a postdoc at the Cancer Research Institute in Heidelberg. In 1985 she became a member of the Basel Institute for Immunology where she stayed until 1991. Her time at the Basel Institute shaped her career significantly, as in this institute young researchers were given complete freedom to choose their research direction thus gaining independence earlier than would otherwise have been possible.
In 1991 Gitta became a group leader in the Division of Molecular Immunology of the Medical Research Council National Institute for Medical Research (now part of the Francis Crick Institute). Her research initially focused on immune tolerance using T cell receptor transgenic mouse models. Following on her interest turned to immunological memory focusing on CD4 memory T cells, their generation and survival.