Italiano: Immune cell populations and the effects of immunosenescence on cellular function. Arrows denote crosstalk/signaling between cell populations, illustrating the potential for dysfunction in a single population to affect the function of numerous other cell subsets. Innate immune cells (neutrophils, macrophages/monocytes, dendritic cells, NK cells) are all involved with signaling and recruitment of other innate cell populations during the early phases of an immune response. Macrophages and dendritic cells bridge the gap from innate to adaptive immunity via antigen presentation and stimulatory signaling to cognate T-cells, and disruption in either of these functions can drastically compromise adaptive responses. Helper T-cells are critical for subsequent development of robust B-cell antibody responses, further illustrating how dysfunction among cells at both the innate and adaptive level can affect the overall outcomes of an immune response.