1. Vyadhikshamatva: Vyadhibala Virodhitva and Vyadhi Utpada Pratibandhakatva

• Vyadhi Utpada Pratibandhakatva corresponds to first-line and pre-existing defences:
  • Innate barriers (skin, mucosa, gastric acid, mucociliary clearance, complement, phagocytes, NK cells).
  • Pre-formed protective antibodies from earlier exposure or vaccination, which are humoral.
  • Memory B and T cells that block infection before disease develops.
• Vyadhibala Virodhitva corresponds to effector responses against an established insult:
  • Cell-mediated immunity: cytotoxic T cells, activated macrophages and Th1 responses clearing intracellular pathogens or abnormal cells.
  • Antibody production and neutralisation, which are humoral.
  • A modulated inflammatory response that limits damage.
• Some commentators link Kapha (Bala), Slaishmika Ojas and Dalhana's "essence of Dhatus" to white blood cells. The same review also notes that the two terms can be mapped differently. I would treat these as analogies, not equivalents.

• Sahaja: innate, genetic, present from birth.
• Kalaja: depends on season (Ritu) and age.
• Yuktikrita: acquired through diet, exercise, Rasayana and treatment.
• Interventions such as Rasayana and Vajikarana belong to Yuktikrita.

2. Factors contributing to Vyadhikshamatva

• Samata (balance) of Vata, Pitta and Kapha keeps the body's defences intact.
• In their normal (Prakrita) state the Doshas support Bala. Kapha in particular is called Balakrit, and Bala is a synonym of Kapha. Kapha in its normal state is Slaishmika Ojas or Apara Ojas, which confers resistance.
• Vitiated Doshas (Vikrita) damage Dhatus, create the Dosha-Dushya binding and lower resistance.
• Doshas that are Prakriti-aligned but strongly aggravated are more likely to cause disease.

• Healthy Dhatus, especially Rasa, Rakta, Mamsa and Meda, which Charaka's Sara assessment refers to, give structural and functional resistance. Each Dhatu's nourishment depends on its own Dhatvagni.
• Dhatu Sara (excellence) and Samhanana (compactness) mark a person who resists disease.
• Charaka (Su. 28/7) lists people who cannot resist disease (Avyadhi-sahani):
  • the very obese and the very emaciated;
  • those with poorly developed muscle, bone and blood;
  • the debilitated;
  • those who eat unsuitable food, or too little;
  • those with weak mental strength (Alpa sattva).
• People with the opposite features resist disease well.

• Jatharagni, Bhutagni and Dhatvagni convert food into Rasa and then into successive Dhatus, ending in Ojas.
• Strong Agni gives good Dhatu quality and Ojas, and Bala follows.
• Weak Agni (Mandagni) produces Ama, which blocks the channels (Srotorodha) and lets Doshas accumulate. Resistance falls and disease develops.
• Related lifestyle factors in the reviews are Ahara, Nidra, Vyayama, Satva and Rasayana.

• Ojas is the essence of all Dhatus and the carrier of Bala. The review describes Ojas as the "inner" aspect and Bala as its functional expression, like mass and energy.
• Para Ojas: about 8 drops, located in the heart. Its loss is fatal.
• Apara Ojas: about half an anjali, circulating through the body.
• Ojas is described as heavy, cool, soft, smooth, thick, sweet, stable, clear, slimy and unctuous.
• Three states of loss:
  • Visramsa: displacement.
  • Vyapat: vitiation.
  • Kshaya: depletion, with fear, weakness, drowsiness, stupor, delirium, muscle wasting and death in severe cases.
• Anything that depletes Ojas lowers Vyadhikshamatva. Causes include fasting, grief, anger, overwork, trauma and chronic disease.

3. Upashaya and Anupashaya, with Ritu and Prakriti

• Upashaya is the practical expression of Satmya. Diet and regimen that suit the individual, the season and the place sustain Agni, Dhatu quality and Ojas, and so protect Vyadhikshamatva.
• Anupashaya, such as eating against one's Prakriti or the season, vitiates Doshas and weakens Agni and Bala.
• Long-standing habits (Okasatmya) can make something harmful tolerable, but harmful habits should be withdrawn gradually, a quarter at a time.

• Kalaja Bala changes with the season. In Visarga Kala (Varsha, Sharad, Hemanta) strength increases. In Adana Kala (Shishira, Vasanta, Grishma) it declines. Resistance is broadly highest in the cold months (Hemanta, Shishira) and lowest in summer and autumn.
• Ritu Satmya, meaning the seasonal diet and regimen (Ritucharya), is therefore Upashaya. For example:
  • Hemanta: heavy, unctuous food, oil massage and exercise, because Agni is strong.
  • Grishma: sweet, cool, liquid food and avoiding strenuous work, because Vata and Bala are depleted.
  • Varsha: light, warm, easily digested food, because Agni is weak and Vata is aggravated.
• Seasonal purification fits the Doshas that accumulate or aggravate: Vamana in Vasanta, Virechana in Sharad and Basti in Varsha.
• Out-of-season or inappropriate regimens (Ritu Asatmya) are Anupashaya.

Evidence note