A new markers for insulin production decline in Type 1 diabetes has been found in the ratio the CD4 naïve (CD45RO-CD62L+) to central memory (CD45RO+CD62L+) and in the level of CD4 central memory T cell subpopulations. A method of diagnosing autoimmunity and its progressiveness more specifically diabetes pre diabetes a susceptibility to diabetes mellitus or the level of effectiveness of therapy/intervention modality for one or more of such conditions in a subject can be conducted by determining level of CD4 naive (CD45RO-CD62L+) T cells by immunofluorescence analysis of a sample extracted from a subject determining level of CD4 central memory (CD45RO+CD62L+) T cells by immunofluorescence analysis of a sample extracted from a subject and quantitatively relating the levels of the CD4 naive and central memory T-cells wherein a low ratio of CD4 naive T-cells to CD4 central memory T-cells and/or high CD4 central memory T-cell indicates autoimmunity a susceptibility to autoimmunity diabetes pre diabetes a susceptibility to diabetes mellitus or ineffectiveness of a treatment for one or more of such conditions.
