Induction of primary immune responses to neoantigens involves the generation of specific T-cells and immunoglobulin M (IgM) antibody secreting B-cells. As part of this process, T and B memory cells are also generated, which have specific cell surface receptors to the antigen. On repeat exposure to the antigen, these memory T- and B-cells are triggered to generate rapid and intense secondary responses. During this secondary response, B-cells secrete abundant specific IgG antibodies with greater affinity to the antigen than for the IgM isotope. This memory response is mediated by T-cells with CD45+ RO+ phenotype. These T-cells provide B-cells the help required to generate the specific IgG. Sub-optimal antibody responses are seen in both acquired and hereditary immunodeficiency, which are due to impaired T-cell function including poor T-helper responses to B-cells and defective neo-antigen responses.