“Know ye not that a little leaven leaveneth the whole lump? Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened.” I Corinthians 5:6, 7

During the time of the early New Testament, the nature of human disease was not well understood. Had Paul been aware of how infections of the body worked, he might well have chosen the analogy of viruses or bacteria to exhort the Corinthians to purge the disease of sin out of their midst. Through the inspiration of the Holy Spirit, however, a strikingly similar analogy does appear in the text that opens this article. The leaven that Paul speaks of is in fact a microorganism—yeast—used to make bread rise during the baking process. Without the active efforts of a baker to keep fresh dough free of yeast, it would become “leavened” and start to rise prematurely. Thus the exhortation: Purge out the old leaven before it spreads!

Bakers, of course, are not the only people interested in controlling the growth of microorganisms. In this article we will examine the means by which our bodies deal with infections from bacteria and viruses as a means to understand the way by which a faithful church addresses false doctrine or practices being introduced into the body of Christ. The God-ordained means by which our bodies remain free of harmful infections is to provide us with an immune system. So, too, God has provided a systematic means to maintain good order in His church, a means by which the body of Christ remains healthy and fruitful in the face of constant threats of infection by sin.

The immune system is a wonderful component of the human body that allows for life in a world that is teeming with potentially harmful viruses, bacteria, and other microbes. Without a functional immune system, we would rapidly succumb to infectious disease. It is no wonder that the symptoms caused by human immunodeficiency virus (HIV) infection—a syndrome we call “acquired immune-deficiency syndrome,” or AIDS—are so feared. When the body lacks immune-defense capacity, it becomes susceptible to infections that are invariably fatal if left untreated. An intact, properly functioning immune system is absolutely indispensable to healthy life in our world.

To understand how this wonderfully fearful system of our body functions, it is important to know a few things about the development and maintenance of the immune system. Like all the other cell types in our blood, the cells of our immune system are produced by stem cells located in the central core of bones that we call the bone marrow. While the stem cells residing in our marrow are not recognizable as any one type of blood cell, they can give rise to the entire hierarchy of cell types found in our blood. Collectively, these cells allow us to carry oxygen (red blood cells), to produce blood clots in response to tissue damage (platelets), and to fight off every conceivable type of foreign invader that can find their way past the external barrier of our skin. This last class of blood cells—which are generically called “white blood cells”—are the major cellular component of the immune system.

The term “white blood cell” actually includes two large subsets of cell types, which can in turn be subdivided into even more specialized types of immune cells. For our purposes, it is sufficient to point out that scientists typically classify white blood cells as being part of either the innate (“built-in”) or the adaptive (“responsive”) immune system. Cells of the innate immune system are constantly roaming the body in search of foreign invaders—usually viruses or bacteria—which they literally gobble up (engulf) and digest as part of their function. This digestive process is incomplete, however, allowing cells of the innate immune system to display molecular pieces of dismembered microbes like trophies on their cell surface as they parade through the vascular system of the body. These molecular trophies serve as a sort of advertisement to other cell types of the adaptive immune system, which subsequently “learn” what to look for as they are recruited to the fight.

Once activated and trained what to look for, the cells of the adaptive immune system become an even more potent army against invading microbes. Unlike the more generalized cells of the innate immune system, which typically destroy anything that looks foreign (whether dead or alive), the cells of the adaptive immune system focus their deadly attacks on the one specific target that they were “trained” to identify. This target is usually a piece of one molecule from a virus or bacterium that was captured and digested by the innate immune cells. Having become alerted to the danger of this foreign molecule, the “activated” cells of the adaptive immune system are able to hunt down and destroy anything that looks like that molecule, including the intact viruses or bacteria on which they are found. This system of “learning” employed by the adaptive immune system can also be engaged therapeutically by the use of vaccines, which put the immune system on alert for a specific invading pathogen without seriously endangering the health of the person being vaccinated. As a result, that person’s immune system is primed to respond rapidly if it encounters the live version of this pathogen.

After being engaged and trained for the fight, cells of the adaptive immune system carry out their attack on invading microbes in a variety of ways. These means of fighting infection include the use of long-range chemical weapons (antibodies) as well as cell-to-cell combat that, like a modern army, can neutralize threats at a distance or at close range. The analogy of an army at war goes even further as other tissues in the body get involved. All tissues are capable of sending out chemical “distress signals” that attract immune cells to the site of active infection. The same biological signals that cause inflammation, swelling, and pain sensations in damaged tissue also serve to recruit immune cells, which rush to the site to carry out the job of destroying foreign invaders. More subtle signals that we are not aware of—called cytokines—are also at play, circulating through the vascular system to constantly inform the dispersed immune system of the condition and integrity of the entire body. In truth, the immune system is an amazing component of the body that functions very much like a resident modern army, always prepared to fight any sort of invader that might cross the outside borders of its host.

There is a valuable analogy between function of the immune system and the way in which the church identifies and perceives threats to her faith and life. Note that these threats are very real and must be correctly combated by the church. What, then, is a correct response? In truth, it looks very much like what our immune systems do when a harmful invader enters the body.

In the first stage of response, the harmful doctrine or practice must be clearly identified as a potential threat to the church. This is one of the essential functions of faithful preaching, which is rightly antithetical in nature, exposing the lies of false doctrine and identifying sinful patterns of living. As such, our first notice of a potential “infection” most often comes from the pulpit through ordained pastors of the Word. As overseers of the preaching, elders in a faithful church are specifically commissioned by Christ to further ensure that false doctrine and practices are not being introduced into the church by those who ought to be bringing the truth of God’s Word (Titus 1:9-11; Jude 1:4). In some circumstances the presence of a doctrinal or practical problem may be first noticed by a perceptive church member functioning in the office of believer, in which case that concern ought to be brought forward to the consistory for proper evaluation and resolution.

Regardless of who first sounds the warning, the church or its members enter the second phase of response when the danger of a doctrinal or practical threat becomes clear. In this second phase, the church rallies the theological resources necessary to expose the specific threat that false doctrine or improper practice poses to the body of Christ. Significant work must be done to educate the church as to the nature and particular danger of this threat and, once again, much of this work falls on the shoulders of officebearers at the “site of infection” in a local church. Their means of exposing error is certainly the light of Scripture, but also the wise counsel of creeds. Let us not forget that many infectious errors in the church of Christ are not new. Like a good vaccine, our creeds provide us with a collective record of prior infections and allow the church to respond quickly when a similar form of that infection emerges. With a clear sense of the danger that has been identified by Scripture and the creeds, the body of Christ can enter into the third phase of responding to false doctrine or practice, which is to clear the infection from its midst.

This third phase must necessarily begin in the local congregation where the infection was first exposed. In many cases, the work of eradicating a false doctrine or practice both begins and ends under the watch of a faithful consistory, which is the goal that is outlined by Paul in many of his epistles to specific congregations. But like an infection that has entered the bloodstream, there are times when error spreads outside the local congregation and becomes a more serious threat to the broader body. In such cases the work of exposing and treating the error becomes the work of an entire denomination in its ecclesiastical bodies, starting at the level of consistories and working up to the level of synod in a Reformed denomination—or their equivalent body in other forms of church government. In the multitude of wise counselors (Prov. 11:14; 15:22), the source of sinful doctrine or practice is directly confronted and combated. Like the immune system, ecclesiastical bodies have a variety of tools at their disposal to fight doctrinal errors. They may directly examine parties involved regarding their orthodoxy or perhaps require a rejection of the error and repentance. In God’s goodness, this action may remove the error from the church. But when these approaches fail to resolve the error, ecclesiastical bodies proceed through the steps of excommunication to remove those who will not submit to the spiritual authority exercised by the church. Whatever the means, the infection of false doctrine or practice is removed so as to maintain health in the body of Christ. This is right and good. It is the way of Scripture (Matt. 18:15-18; I Cor. 5).

In conclusion, I point readers to the Synod of Dordt (1618-19), which is celebrating its 400th anniversary this year and next. The work done at this ecclesiastical assembly is a clear example of the church uniting all of its theological resources to eradicate the deadly infection of Arminianism that had crept into the Dutch Reformed churches. Four hundred years later we continue to treasure the central work of this synod—its Canons—as a living “vaccine” for the threat of the Arminian infections that continue to emerge in the modern church world. Thank God that He has given both our physical bodies and the body of Christ a means to combat infections! The immune system is indeed an amazing aspect of our being “fearfully and wonderfully made,” which ought to turn us to our Creator in praise and worship.

The Lord willing, we will continue to build on the analogy between the immune system and the church in the next article in this series, considering other aspects of similarity, albeit from a different perspective.