Immune cycle

The immune cycle is a term that describes a natural homeostatic oscillation of the immune system when chronic inflammation is occurring. Similar to the menstrual cycle, the exact wavelength and waveform of each particular individual patient is different. That is, different people have different immune cycles although each cycle is typically repeated every seven days.

C-reactive protein levels in the blood need to be measured every few days in order to have enough time points to show a repeating fluctuation (a wave-like cycle). This is caused by the synchronous division of T cells over time, with T-effector cells boosting immune activity followed by T-regulatory cells suppressing the immune response.

Although the exact reason for the immune cycle is not yet clear, it appears to be a result of repeating and alternating stimulation and inhibition of the immune response, which has been demonstrated to exist in cancer patients. Many cycles occur in the body - like temperature regulation and hormone levels - and the exact cause for these cycles is also unknown, but it is thought to involve the hypothalamus.

The process used to identify this cycle is called 'immune cycle mapping', while the process that uses this cycle in treatment is called 'immune synchronisation'. It is important to note that the immune cycle and immune synchronisation still "require a lot more testing" before treatment methods can become viable because the "research is still in its early stages".

The idea of an immune cycle has existed for well over a hundred years. In 1891, Dr William Coley noticed that some of his patients responded better to treatment than other patients, even with complete responses. Almost a century later, in 1975, physicist George Irving Bell developed a mathematical equation to predict a hypothetical immune cycle. Dr Robert North, writing in the 1980s, demonstrated that chemotherapy encouraged the growth of tumors in mice, whose immune systems are very similar to humans. Unfortunately, these pioneers of the immune cycle were unable to establish its existence, particularly since the necessary technology had not yet come into existence.

In the late 1990s, Associate Professor Brendon Coventry noticed that some of his patients responded better to a Melanoma vaccine than other patients despite receiving identical treatment. When local cancer tumours where injected with the vaccine, cancers that had not been injected began to shrink as well, thus indicating an immunogenic relationship. These observations led him to speculate that the immune system operates in a cyclical manner, with peaks and troughs. Operating on this theory, Coventry was able to increase complete response rates to treatment of advanced melanoma from 7% to 17% and without noticeable negative side effects to chemotherapy and radiotherapy.

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